chore(hygiene): purge committed build artifacts + fix Secret Scanner startup_failure (#341)

## What

Three mechanical hygiene items from the 2026-07-07 ground-truth health
check:

1. **Closes #267** — removes the 369 `.zig-cache-global/` build-artifact
files that were committed against the (already present) gitignore rule.
2. **OCaml artifacts** — removes committed `.cmi`/`.cmo` compiled
artifacts and gitignores the pattern. The `.ml`/`.mll`/`.mly` **sources
are untouched** — their keep-or-delete call is #265 (owner decision,
unchanged).
3. **Secret Scanner startup_failure** — `secret-scanner.yml` (and
`mirror.yml`) still pinned the standards reusable at `d135b05`, the
known-broken estate SHA; every push to main has startup_failure'd since.
Repinned to `d7c2271`, matching all other workflows (PR #328's repin
missed these two). This PR's own checks demonstrate the fix.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: hyperpolymath

.github/workflows/mirror.yml

@@ -11,5 +11,5 @@ permissions:
 
 jobs:
   mirror:
-    uses: hyperpolymath/standards/.github/workflows/mirror-reusable.yml@d135b05bfc647d0c0fbfedc7e80f37ea50f49236
+    uses: hyperpolymath/standards/.github/workflows/mirror-reusable.yml@d7c22711e830e1f383846472f6e9b99debdb201e
     secrets: inherit

.github/workflows/secret-scanner.yml

@@ -15,5 +15,5 @@ permissions:
 
 jobs:
   scan:
-    uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@d135b05bfc647d0c0fbfedc7e80f37ea50f49236
+    uses: hyperpolymath/standards/.github/workflows/secret-scanner-reusable.yml@d7c22711e830e1f383846472f6e9b99debdb201e
     secrets: inherit

.gitignore

@@ -92,3 +92,8 @@ deps/
 .elixir_ls/
 .cache/
 dist/
+
+# OCaml build artifacts (issue #265 sources pending; artifacts never belong)
+*.cmi
+*.cmo
+*.cmx