ADR-0027: existing-cases sweep + docs (step F)

Sweep: input_verdict tests confirm the schema-existence check
fires across the identifier-taking commands — unknown table
on drop / show / add column, unknown column on drop column /
update — and that known references stay clean. The Step B
check is grammar-generic, so this is verification + coverage
rather than new code.

Docs: requirements.md S6 -> [x], baseline 1096; CLAUDE.md
deferred list reconciled (C5a and S6 are done — removed);
ADR-0026's as-built note updated (step 5 shipped via
ADR-0027); ADR-0027 gains an As-built notes section
recording the post-walk diagnostics realization, the
pre-rendered message, the timeout-based debounce, coarse
WARNING spans, and the deferred highlight/hint wiring.

docs/adr/0026-complex-where-expressions.md

@@ -462,19 +462,20 @@ choices, and where they deviate from the design sketch above:
   column's type, exactly as the pre-ADR `where col = val`
   slot did. The operand grammar carries no validators —
   permissive per §7.
-- **Step 5 deferred to ADR-0027.** The §7 *behaviour*
-  relaxation is done: `bind_where_literal` binds a
-  type-mismatched WHERE literal by its syntactic shape, and
-  the pre-ADR bind-time rejection is gone. The §7
-  *diagnostic flagging* — surfacing a type-mismatched
-  comparison or `= NULL` as an error-class highlight + hint
-  — is the seam with ADR-0027, which designs the walker
-  diagnostics-severity model that flagging belongs in (and
-  whose WARNING severity is defined to have "no triggers
-  until ADR-0026 is implemented"). Building the flagging as
-  a standalone mechanism first would be reworked by
-  ADR-0027; the recommendation is to implement it as the
-  first triggers of ADR-0027's model.
+- **Step 5 — done, as part of ADR-0027.** The §7
+  *behaviour* relaxation landed with steps 1–4:
+  `bind_where_literal` binds a type-mismatched WHERE literal
+  by its syntactic shape, and the pre-ADR bind-time
+  rejection is gone. The §7 *diagnostic flagging* — a
+  type-mismatched comparison or `= NULL` as a flagged
+  finding — was folded into ADR-0027's walker
+  diagnostics-severity model rather than built as a
+  standalone mechanism (ADR-0027's WARNING severity is
+  defined to have "no triggers until ADR-0026 is
+  implemented" — those triggers are exactly these). It
+  surfaces as a `Severity::Warning` `Diagnostic`, computed
+  post-walk from the built `Expr` against the table's
+  column types — see ADR-0027.
 
 ## See also
 

docs/adr/0027-input-validity-indicator.md

@@ -229,6 +229,66 @@ ADR-0026's expression diagnostics (type mismatch, `= NULL`)
 land with that ADR's implementation and feed the WARNING
 severity.
 
+## As-built notes (2026-05-19)
+
+All five build-order steps are implemented, and — because
+ADR-0026 deferred its own step 5 — the ADR-0026 §7
+expression diagnostics (type mismatch, `= NULL`) were folded
+in here as the WARNING severity's first triggers. Realization
+choices and deviations from the sketch above:
+
+- **Diagnostics are computed post-walk, not emitted during
+  the walk.** §2 says "diagnostics are emitted there [in the
+  walker]". As built, the walk produces the `MatchedPath` and
+  the `Command` as before; `walk()` then runs two post-walk
+  passes — `schema_existence_diagnostics` over the matched
+  path, and `expr_warnings` over the built `Expr` — and
+  stores the result in `WalkResult::diagnostics`. This keeps
+  diagnostics off the walker's speculative-rollback paths
+  (a `Choice` branch that matches an ident then rolls back
+  would otherwise leak a diagnostic); the post-walk passes
+  see only the surviving terminals. Same single schema-aware
+  context, one logical pass later.
+- **`Diagnostic` carries a pre-rendered `message: String`,**
+  not the `{severity, span, message_key}` of §2. Each
+  diagnostic source catalog-translates at creation. This
+  sidesteps the awkwardness of a parse-style message having
+  no single static key, and the model stays "roughly
+  `{severity, span, message}`".
+- **The parse outcome is not a synthetic `Diagnostic`.** The
+  indicator reads it straight from `WalkOutcome` (§2's
+  "highest severity across the outcome *and* the
+  diagnostics"); `diagnostics` carries only the schema-aware
+  findings layered on a structurally-valid parse. Schema-
+  existence therefore runs only on a `Match`.
+- **`MatchedKind::Ident` gained an `IdentSource` field** so
+  the post-walk schema check can tell a table reference from
+  a column reference from an invented name without
+  hard-coding role strings.
+- **The debounce uses `tokio::time::timeout` per event-loop
+  iteration,** not `tokio::select!` — it keeps the existing
+  ~100-line event-handler body un-reindented. `recv` is
+  time-boxed only while a recompute is owed; an idle session
+  still blocks plainly. Any event resets the window (not
+  only keystrokes) — a slight over-reset, harmless in
+  practice.
+- **WARNING spans are coarse** — the whole WHERE clause. The
+  `Expr` AST carries no source spans, and the indicator
+  reads only severity. Precise per-literal spans (for a
+  future warning-highlight overlay) are a refinement.
+- **Highlight / hint integration beyond the indicator** —
+  §2 notes highlighting and the hint panel "read the
+  individual diagnostics". The indicator and the model
+  ship; routing diagnostic spans into the per-byte highlight
+  overlay, and diagnostic messages into the hint panel
+  beyond the existing parse-error path, is a follow-up (the
+  build order did not enumerate it as a step).
+- **Debounce timing is not unit-tested** — it is async
+  event-loop glue. `App::input_validity_verdict` (the pure
+  verdict) and the indicator rendering are covered;
+  `input_verdict` has a parse-outcome / schema-existence /
+  expression-warning / existing-cases-sweep test set.
+
 ## See also
 
 - ADR-0003 — input modes; the input field and its mode

docs/requirements.md

@@ -26,13 +26,14 @@ repo is pushed).
 
 ## Test baseline
 
-After ADR-0026 steps 1–4 (complex WHERE expressions):
-**1070 passing, 0 failing, 1 ignored** (`cargo test` — the
-one ignored test is a long-standing `` ```ignore `` doc-test
-in `src/friendly/mod.rs`). Clippy clean with the nursery lint
-group enabled. (Earlier reference points: 1039 after ADR-0025
-(indexes); 1006 after ADR-0024 + the handoff-14 cleanup; 449
-after B2/C2.)
+After ADR-0027 (input-validity indicator): **1096 passing,
+0 failing, 1 ignored** (`cargo test` — the one ignored test
+is a long-standing `` ```ignore `` doc-test in
+`src/friendly/mod.rs`). Clippy clean with the nursery lint
+group enabled. (Earlier reference points: 1079 after ADR-0026
+(complex WHERE expressions); 1039 after ADR-0025 (indexes);
+1006 after ADR-0024 + the handoff-14 cleanup; 449 after
+B2/C2.)
 
 ---
 
@@ -60,12 +61,18 @@ after B2/C2.)
   for inspecting hints about the current input or last error.
 - [ ] **S5** Mode label and distinct border style on the input
   field communicate the current input mode at all times.
-- [ ] **S6** Input-field validity indicator: a debounced
+- [x] **S6** Input-field validity indicator: a debounced
   `[ERR]` / `[WRN]` marker at the right edge of the input row,
   summarising — before submit — whether the current command
   would run. Backed by a walker diagnostics-severity model
   (ERROR / WARNING). Advisory only — never blocks submission.
-  Designed in ADR-0027; implementation pending.
+  *(ADR-0027: `Severity` / `Diagnostic` on `WalkResult`;
+  `input_verdict` combines the parse outcome, schema-existence
+  ERRORs — unknown table / column — and the ADR-0026 §7
+  expression WARNINGs — type mismatch, `= NULL`. The runtime
+  debounces the indicator's display ~1 s; the rightmost six
+  columns of the input row are reserved unconditionally. New
+  `warning` theme colour.)*
 
 ## Input field