docs: session handoff 47 + M4 update — DSL→SQL echo Phase 1 (Bucket A) done

docs/requirements.md

@@ -120,19 +120,29 @@ handoff-14 cleanup; 449 after B2/C2.)
   one-shot advanced escape (with the prompt label updated). The
   `mode simple` / `mode advanced` command switches modes
   persistently.
-- [~] **M4** Execution-time mode side-channel — deferred, awaiting
-  its own ADR (ADR-0033 Amendment 3). Every command should know, at
-  execution time, which of three modes it ran under — `simple`,
-  `advanced`, or `advanced-one-shot` (the `:` escape) — so execution
-  can adjust *output* without changing command *identity* (e.g. a
-  simple-mode `create table` echoing the generated SQL when run in
-  advanced mode, silent in simple). Today only the *rendering*
-  side-channel exists (`OutputLine.mode_at_submission`); the `Mode`
-  enum is two-way, the one-shot distinction is collapsed at
-  submission, and neither `Action::ExecuteDsl` nor the worker carries
-  any mode. The work widens `Mode` to three-way and threads it
-  through the `Action` → worker interface. Not required for Phase 3
-  dispatch correctness; tracked here so it is not lost.
+- [x] **M4** Execution-time mode side-channel — **implemented** via
+  ADR-0037 (the channel) and its motivating consumer ADR-0038 (the
+  DSL → SQL teaching echo). Every command knows, at execution time,
+  which of three modes it ran under — the three-way
+  `EffectiveMode` { `Simple`, `AdvancedPersistent`,
+  `AdvancedOneShot` } resolves at submit time and threads through
+  `Action::ExecuteDsl` → runtime; the persistent `Mode` enum stays
+  two-way (the transient one-shot `:` lives on the channel where it
+  belongs, not in persistent state). The runtime gates the
+  ADR-0030 §10 teaching echo on it: a DSL-form command run in
+  advanced/one-shot mode renders the equivalent advanced-mode SQL
+  beneath `[ok]`; simple-mode and SQL-entered submissions stay
+  silent. Echo coverage progress: **Bucket A complete** (Phase 1 —
+  single-statement DDL + `show data` + `--all-rows` fall-throughs,
+  every row round-tripped per ADR-0038 §1; handoff-47);
+  **Bucket B** (resolved-name + multi-line echoes — `add index`,
+  relationship add/drop, `drop column --cascade`,
+  `add relationship --create-fk`) and **category-3 prose**
+  (`shortid` generation, type-conversion transforms,
+  `change column --dont-convert` caveat) are deferred to Phase
+  2 / Phase 3 per ADR-0038 §8. The de-emphasised styled-runs
+  rendering polish (ADR-0038 §4 / ADR-0028) is also still pending —
+  the echo currently surfaces as a plain `[system]` line.
 
 ## App-level commands (per ADR-0003)