feat: planner parse-the-bytes-you-inline gate (issue #1 Fix 4)

Adds self-review check #9 to planner Step 5, symmetric to Fix 1: when
the profile declares `spec_validation.parsers`, every verbatim code
body the plan inlines into a task step whose fence label has an entry
must parse clean against the live tool before hand-off. Non-zero exit
is a plan failure — the last defensive line before implementer
dispatch. Trace goes into the planner session.

Targets the surface-language snippets the plan lifts verbatim from the
spec (the compound-hallucination bytes); source-language test/impl
bodies are out of scope — the implement compile gate catches those.

Also adds a Common Rationalisation ("came straight from the spec") and
a Red Flag (configured parser, no trace in session).

refs #1

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

planner/SKILL.md

@@ -221,6 +221,26 @@ Before handing the plan off, run this checklist inline:
    so "nothing ran" cannot masquerade as "nothing
    regressed". This is a recurring defect family — scrub
    every Run step whose assertion lives in a filter string.
+9. **Parse-the-bytes-you-inline gate.** If the project profile
+   declares `spec_validation.parsers`, every verbatim code body
+   the plan inlines into a task step whose fence label has a
+   `parsers` entry must be parsed clean against the live tool
+   before hand-off. For each such block: write it to a temp file
+   with the entry's `ext`, run the entry's `cmd` with `{file}`
+   substituted, require exit 0. A non-zero exit is a plan failure
+   — the plan would hand the implementer bytes that do not parse,
+   the last defensive line before dispatch — fix the plan, do not
+   hand off. The parse-trace goes into the planner's self-review
+   activity (the session) as the attestation the gate fired. The
+   target is the surface-language snippets the plan lifts verbatim
+   (example programs, fixtures); the project's source-language
+   test / implementation bodies are NOT the target — the
+   `implement` compile gate catches those. A block whose fence
+   label has no entry is skipped and the skip noted ("no parser
+   for fence label X"); never a silent pass. A malformed entry
+   (`cmd` without `{file}`, or `ext` / `cmd` missing) is a profile
+   error to surface, not a skip. If the profile declares no
+   `spec_validation`, this check is a documented no-op.
 
 Fix issues inline.
 
@@ -252,6 +272,7 @@ The planner skill does not perform the commit itself.
 | "Step 5 'implement the parser' is fine, I'll detail it at execution time" | Then it's not a step, it's a wish. Steps are bite-sized OR the plan isn't done. |
 | "Task 7 is similar to Task 4, just say so" | The executor may read tasks out of order. Repeat the code. |
 | "The spec has a TBD too, I can pass it through" | Bounce back to `brainstorm`. Plans inherit spec gaps; spec gaps are not plan placeholders. |
+| "The example program came straight from the spec, it must be valid" | The spec's code blocks are hypotheses, not verified bytes — brainstorm's parse gate can be skipped and a post-spec edit can break them. Re-parse every surface-language body you inline; this is the last line before the implementer hits it (issue #1 Fix 4). |
 
 ## Red Flags — STOP
 
@@ -262,6 +283,9 @@ The planner skill does not perform the commit itself.
 - Step descriptions longer than the code they describe
 - Header missing parent spec reference
 - Self-review skipped because "the plan looks fine"
+- A task step inlining a surface-language code body whose fence
+  label has a configured `spec_validation` parser, handed off
+  without a parse-trace in the planner session
 
 ## Cross-references