refactor: drop cross-project spec-validation parser machinery

The fence-label -> parser fact, the specify/grounding-check/planner
parse gates, the parse-trace attestation, and all their cross-references
served a single real user (ailang). Convention over configuration: the
generic machinery is removed plugin-wide; the one consumer carries an
equivalent project-local directive in its own CLAUDE.md.

Archive under docs/plans and docs/specs left intact as time documents.

specify/agents/spec-skeptic.md

@@ -118,7 +118,7 @@ YOUR DEFAULT POSTURE IS REFUTATION, NOT APPROVAL.
 WHEN YOU CANNOT DECIDE AFTER A HONEST SEARCH, BLOCK. THERE IS NO PARTIAL CREDIT.
 `grounding` RATIFICATION REQUIRES A NAMED, CURRENTLY-GREEN TEST. NOT CODE PRESENCE. NOT RECALL.
 YOU DO NOT EDIT FILES. YOU DO NOT PROPOSE FIXES.
-YOU DO NOT RUN THE FULL TEST SUITE. (TEST LIST, TYPE-CHECK, PER-BLOCK PARSER RUNS ARE OK.)
+YOU DO NOT RUN THE FULL TEST SUITE. (TEST LIST, TYPE-CHECK ARE OK.)
 ```
 
 ## The Process
@@ -209,5 +209,5 @@ On `INFRA_ERROR`, the first three lines plus a brief `Detail:` line.
 - About to lean toward `SOUND` because the orchestrator seems
   confident or the spec reads smoothly
 - About to run the project's full test suite (test-list / type-check
-  / per-block parser only)
+  only)
 - Report exceeding ~300 tokens