docs(hint): defer pre-submit-diagnostic route + diagnostic.* blocks (ADR-0053)

Phase C scope decision: Diagnostic carries no class key, so the F1
diagnostic route would need a class field threaded through every
diagnostic site (broad change) for marginal value — tier-2 already
surfaces diagnostics and many duplicate the runtime error classes. Defer
the route + the ~33 diagnostic.* tier-3 blocks to issue #38. v1 ships
command-form hints + 9 runtime error-class hints (comprehensive for
those). Updates ADR-0053 D2/D6/Status/OOS + README.

docs/adr/0053-contextual-hint-command-and-keybinding.md

@@ -10,10 +10,13 @@ Phase B implementation (2026-06-15): the first exemplar showed per-*node*
 keying is too coarse for multi-form commands (`add`/`drop`/`show`/
 `create`), so D3 now keys tier-3 content **per form** via a
 `hint_ids: &[&str]` array mirroring `usage_ids` — and **clause-concept
-hints** are recorded as a deferred extension (separate tracking issue).
-The parallel question of whether the in-app `help` command should
-likewise distinguish advanced-SQL forms is tracked **separately** as
-Gitea issue #36 (it touches shipped, ADR-backed `help` behaviour).
+hints** are recorded as a deferred extension (issue #37). During Phase C
+the **pre-submit-diagnostic route + the ~33 `diagnostic.*` blocks** were
+**deferred** (issue #38) — `Diagnostic` doesn't carry its class key, so
+the route needs a broad change for marginal value (D6). v1 therefore
+ships command-form hints + the 9 runtime error-class hints. The parallel
+question of whether the in-app `help` command should likewise distinguish
+advanced-SQL forms is tracked **separately** as Gitea issue #36.
 
 Decided in conversation 2026-06-14. Closes the last open piece of **A1**
 (the canonical app-command set, ADR-0003): every app command is
@@ -112,19 +115,13 @@ F1 is inert behind a modal and while a sidebar panel holds navigation
 focus (consistent with the existing `handle_key` gates, ADR-0046); it is
 active in the input context in both Simple and Advanced mode.
 
-**Two error sources, one namespace.** Errors come in two kinds and reach
-`hint` by different routes:
-
-- **Pre-submit diagnostics** (the ~33 `diagnostic.*` classes — arity,
-  type, unknown table/column) are computed *while typing* by the walker.
-  The **F1 live-input path** reads the current under-cursor diagnostic
-  directly from the walker (the same source the ambient panel uses) and
-  renders its `hint.err.<class>` block — no stored state needed.
-- **Runtime errors** (the 9 `translate_error` classes) occur *after*
-  submit. The **`hint` command / empty-input F1** path reads them via the
-  stored `last_error_hint_key` (D5).
-
-Both render from the same `hint.err.*` namespace. **`:`-prefix handling:**
+**Error routes.** **Runtime errors** (the 9 `translate_error` classes)
+occur *after* submit; the **`hint` command / empty-input F1** path reads
+them via the stored `last_error_hint_key` (D5) and renders their
+`hint.err.<class>` block. (A second route for **pre-submit diagnostics**
+on the F1 live-input path was specified but is **deferred** — D6 / issue
+#38; with a diagnostic present, F1 shows the command block and tier-2
+shows the diagnostic.) **`:`-prefix handling:**
 on the simple-mode one-shot escape (`: SELECT …`), command
 identification for the F1 path strips the leading `:` first, so the
 advanced form is matched.
@@ -220,26 +217,37 @@ Option<String>`** — set at the `translate_error` call sites
 cleared when a later command succeeds. Absent → the "getting started"
 pointer.
 
-The **pre-submit-diagnostic route** (the F1 live-input path) needs no
-stored state: it reads the current diagnostic from the walker at F1 time
-(D2). This is the cleaner split the `/runda` pass surfaced — typing-time
-diagnostics and post-submit runtime errors are genuinely different
-sources and should not be funnelled through one stored key.
+The **pre-submit-diagnostic route** (the F1 live-input path reading the
+under-cursor diagnostic) is **deferred** — see the scope note in D6.
 
-### D6 — Content scope: comprehensive for v1
+### D6 — Content scope for v1
 
-v1 ships tier-3 content for the **whole inventory**, not a subset (the
-graceful tier-2 fallback below is a safety net, not the plan):
+v1 ships tier-3 content for the **command forms and runtime error
+classes** — comprehensive for those (the graceful tier-2 fallback below
+is a safety net, not the plan):
 
 - **~37 command forms** — every distinct node in `REGISTRY` gets its own
   `hint.cmd.<hint_id>` block (app + DSL + DDL + advanced-mode SQL forms),
   each with a **mode-correct example** (the advanced-SQL forms show SQL
   syntax, their simple siblings show DSL — no sharing).
-- **9 runtime error classes** — `unique`, `foreign_key` (×4 sides),
-  `not_null`, `check`, `type_mismatch`, `not_found`, `already_exists`,
-  `generic`, `invalid_value` — each gets a `hint.err.*` block.
-- **~33 `diagnostic.*` pre-submit classes** — arity, type, unknown
-  table/column, etc. — each gets a `hint.err.*` block.
+- **9 runtime error classes** — `unique`, `foreign_key` (child/parent
+  side), `not_null`, `check`, `type_mismatch`, `not_found`,
+  `already_exists`, `generic`, `invalid_value` — each gets a
+  `hint.err.*` block.
+
+**Deferred — the ~33 `diagnostic.*` pre-submit classes and the F1
+diagnostic route** *(Phase C scope decision, 2026-06-15; issue #38)*. The
+original "comprehensive" scope included them, but implementation revealed
+`Diagnostic` (`walker/outcome.rs`) carries only its rendered `message`,
+not its class key — so a live diagnostic can't be mapped to
+`hint.err.<class>` without adding a `class` field threaded through every
+diagnostic-creation site (a broad change). Weighed against the value, it
+isn't worth it for v1: pre-submit diagnostics are already surfaced by
+tier-2 (ambient message + validity indicator, ADR-0027); F1 still shows
+the useful command block when a diagnostic is present; and many
+diagnostic classes duplicate runtime classes already covered
+(`type_mismatch`, `unknown_table`↔`not_found`, arity↔`invalid_value`).
+Deferred to issue #38, additively (the keying doesn't lock it out).
 
 The full enumerated checklist is the implementation plan's tracking
 artifact (see *Content inventory*, below).
@@ -339,26 +347,26 @@ Hint — add relationship
   `App` state (`last_error_hint_key`), and one new renderer family
   (`note_hint*`); the `AppCommand` enum gains `Hint`, the grammar a `HINT`
   node, the REGISTRY one entry.
-- **A large, durable content corpus** (~37 command blocks + ~42 error/
-  diagnostic blocks ≈ 80) enters the catalogue under `hint.cmd.*` /
+- **A durable content corpus** (~37 command blocks + 10 runtime
+  error-class blocks) enters the catalogue under `hint.cmd.*` /
   `hint.err.*`, validated by `keys.rs`. This is ongoing surface area: new
   commands/error classes should ship with their tier-3 hint (a checklist
-  item for future feature ADRs).
+  item for future feature ADRs). (Diagnostic-class blocks deferred — #38.)
 - **Testing:** Tier-1 unit tests for the trigger matrix (F1 with
   empty/non-empty input; `hint` with/without a recent error;
   `last_error_hint_key` set on the `translate_error` sites and cleared on
-  success; the pre-submit-diagnostic vs runtime-error routing; the `:`
-  strip), the command-identification logic, and the tier-2 fallback;
-  Tier-2 `insta` snapshots for a representative rendered hint block;
-  Tier-3 integration tests for the end-to-end flows (type a partial
-  command → F1 → block appears, **buffer and completion memo untouched**;
-  run a failing command → `hint` → error expansion). **A
-  comprehensiveness coverage test** (enforces D6): iterate the REGISTRY
-  and assert every node has a `hint_id` resolving to a `hint.cmd.*` block,
-  and every runtime-error/diagnostic class has a `hint.err.*` block —
-  `keys.rs` only checks that *referenced* keys resolve, not that every
-  command/error *has* one, so this test is what makes "comprehensive"
-  enforceable rather than aspirational.
+  success; the mode-aware form resolution; the `:` strip), the
+  command-identification logic, and the tier-2 fallback; Tier-2 `insta`
+  snapshots for a representative rendered hint block; Tier-3 integration
+  tests for the end-to-end flows (type a partial command → F1 → block
+  appears, **buffer and completion memo untouched**; run a failing
+  command → `hint` → error expansion). **A comprehensiveness coverage
+  test** (enforces D6): iterate the REGISTRY and assert every node with a
+  `hint_ids` entry resolves to a `hint.cmd.*` block, and every runtime
+  error class resolves to a `hint.err.*` block — `keys.rs` only checks
+  that *referenced* keys resolve, not that every command/error *has* one,
+  so this test is what makes the scope enforceable rather than
+  aspirational. (Diagnostic classes are out of this scope — D6 / #38.)
 
 ## Out of scope
 
@@ -381,6 +389,11 @@ Hint — add relationship
   recognized clause, deeper than tier-2's candidate list but narrower than
   the per-form block. Per-form keying (D3) does not lock it out. To be
   tackled as a deliberate follow-up job, not gated on usage statistics.
+- **Pre-submit-diagnostic route + `diagnostic.*` tier-3 blocks** — OOS
+  (deferred, issue #38): needs a class field on `Diagnostic` threaded
+  through every creation site (broad change) for marginal value, since
+  tier-2 already surfaces diagnostics and many duplicate runtime classes
+  (D6).
 
 ## Content inventory (implementation tracking)
 
@@ -401,4 +414,5 @@ The implementation plan enumerates and checks off every block:
 - **`hint.err.*`** — one per runtime error class (`unique`,
   `foreign_key.{child,parent}_side`, `not_null`, `check`,
   `type_mismatch`, `not_found`, `already_exists`, `generic`,
-  `invalid_value`) and per `diagnostic.*` pre-submit class.
+  `invalid_value`). The `diagnostic.*` pre-submit classes are **deferred**
+  (D6 / issue #38).