docs(provenance): migrate the corpus to the Research registry grammar

Repoint every `Research doc:` at the plugin's Research registry
(git/sources.md, pre-commit/sources.md, gitea/sources.md,
agentsmd/sources.md), keeping the old topic-doc link as a parenthetical
`(digest: ...)` annotation. Brace expansions and the gitea-releases
semicolon pair collapse to one path.

Entries with no registry (org-commit-conventions, org-git-conventions,
governance-secrets-hard-prohibition, adr-0002-0003-two-tier-claude-md)
now declare `none` plus `Basis:` bullets. The two git entries cite
core/instructions/git.md and commits.md as `(removed in 5deed07)`.

Remove the house-vale-3-15-2-repro entry and its source_keys citations
from vale-config and vale-run. It claimed six behaviours were reproduced
against purpose-built fixtures in this repo, but the entry was added in
d1afdbe with no test or fixture files, and none exists in history. The
behavioural rules stay; only the unbacked provenance claim goes.

Refs: #121
ADR: 0028
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EGHFJextYtVQseaHPDDhxB

plugins/git/.apm/skills/git-submodules/references/sources.md

@@ -10,7 +10,7 @@ source_keys:
 
 **Source:** https://git-scm.com/docs/git-submodule
 
-- **Research doc:** plugins/git/docs/research/docs/git/submodules.md (whole-document reference — the research doc is organized by descriptive prose headings such as "Concept Overview" and "Key Commands" rather than a heading matching this slug; this key covers the entire doc, not a single section)
+- **Research doc:** plugins/git/docs/research/docs/git/sources.md (digest: plugins/git/docs/research/docs/git/submodules.md — whole-document reference — the research doc is organized by descriptive prose headings such as "Concept Overview" and "Key Commands" rather than a heading matching this slug; this key covers the entire doc, not a single section)
 
 **Contributing files:**
 - SKILL.md (all sections)