fix(hint): correct H2 corpus errors + add parse guard (handoff-71)

Semantic verification pass over the tier-3 `hint` corpus (ADR-0053).
Four content errors corrected in src/friendly/strings/en-US.yaml:

- cmd.create_table: the example `with pk id(serial), name(text),
  email(text)` declares a 3-column COMPOUND primary key, not a PK
  plus regular columns (every `with pk` column is a key member,
  ADR-0005). Rewritten to a single-column PK + `add column` for the
  rest; what/concept aligned.
- cmd.save: `save as my-shop` does not parse — `save as` takes no
  inline name, it opens a path-entry prompt. Example -> `save as`;
  what no longer implies inline naming; added a temp-vs-named concept.
- cmd.import: target `shop-copy` does not parse — the `as <target>`
  slot is a NewName ident that rejects hyphens. -> `shop_copy`.
- err.foreign_key.child_side: dropped the bogus `on delete set
  null/cascade` remedy — that governs the parent direction; a
  child-side violation is fixed by inserting the parent first
  (matches the tier-1 hint).

Adds every_cmd_hint_example_parses_in_its_mode — a catalog-driven
guard that parses every hint.cmd.* example in its taught mode,
backstopping syntactic drift (it caught the save and import errors).
Registers the new hint.cmd.save.concept key.

docs: drop two stale "deferred" entries from CLAUDE.md — project
storage (export/import, --resume, input history, migration scaffold)
and m:n convenience (C4) are all implemented (ADR-0015/0045); record
the verification pass on requirements.md H2.

docs/requirements.md

@@ -820,7 +820,12 @@ since ADR-0027.)
   (`what`/`example`/`concept`) covers every command form + the 9 runtime
   error classes, enforced by a comprehensiveness coverage test. Deferred:
   the pre-submit-diagnostic route + `diagnostic.*` blocks (#38),
-  clause-concept hints (#37).)*
+  clause-concept hints (#37). **Content verified 2026-06-15 (handoff-71):**
+  a semantic pass over every `hint.cmd.*`/`hint.err.*` block fixed four
+  errors — `create_table` (compound-PK misread), `save` (no inline name),
+  `import` (hyphen-rejecting target), and `foreign_key.child_side` (wrong
+  `on delete` remedy) — and added a catalogue-driven guard test that parses
+  every command example in its taught mode.)*
 - [x] **H3** `help` provides general reference and per-command
   help.
   *(Done 2026-06-07: the **general reference** is `help` (no arg) —