docs(exemptions): align Layer-4 references with .affine source / .deno.js runtime

Mirrors the workflow swap in this PR. Three updates to
`docs/EXEMPTION-MECHANISMS.adoc`:

1. Layer 4a description — point at `scripts/check-ts-allowlist.affine`
   as the source of truth, note the compiled `.deno.js` is what the
   workflow actually runs.

2. History — add a fourth bullet covering standards#283 / #310 / #311:
   the TS→AffineScript port arc, with the dual-target rationale spelled
   out (`.ts` kept for regression suite + parallel-validation; `.deno.js`
   is the workflow target).

3. Cross-references — replace the single `.ts` line with three lines
   covering all three files (.affine source / .deno.js runtime / .ts
   archetype) and what each is for. Reduces "which file should I edit?"
   ambiguity for the next contributor.

No behavioural change; pure doc alignment so the prose matches the
workflow + source layout after #311 lands.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

docs/EXEMPTION-MECHANISMS.adoc

@@ -137,8 +137,10 @@ across the estate. Three sub-layers:
 
 === 4a: Built-in path / filename allowlist
 
-Hard-coded in `scripts/check-ts-allowlist.ts`. Covers paths that are
-*always* exempt regardless of per-repo configuration:
+Hard-coded in `scripts/check-ts-allowlist.affine` (source of truth;
+compiled to `scripts/check-ts-allowlist.deno.js` which the workflow
+invokes). Covers paths that are *always* exempt regardless of per-repo
+configuration:
 
 * Directory segments: `bindings`, `tests`, `test`, `scripts`,
   `mcp-adapter`, `cli`, `vendor`, `examples`, `ffi`, `node_modules`,
@@ -230,11 +232,23 @@ sufficient. Most repos will pick one or the other.
   + new typed-infrastructure file. Owner picked the Layer-2.5 approach
   (standards#185) over the minimal regex-only fix (standards#183).
   This document seeds the doctrine.
+* AffineScript port (standards#283 seed, #310 compile/runtime fixes,
+  #311 workflow swap): `.ts` → `.affine` self-referential port under
+  the TS→AffineScript campaign (#239 / #241 STEP 2). The `.ts`
+  archetype is kept for the regression suite and parallel-validation;
+  the workflow now runs the compiled `.deno.js`. Retirement of the
+  `.ts` is a follow-up after the dual-target window.
 
 == Cross-references
 
 * `docs/HYPATIA-BASELINE-FORMAT.adoc` — the baseline file format.
 * `.machine_readable/hypatia-baseline.schema.json` — machine schema.
-* `scripts/check-ts-allowlist.ts` — the Deno detector behind Layer 4.
+* `scripts/check-ts-allowlist.affine` — the AffineScript source of
+  truth for the Layer 4 detector (since standards#283 / #310 / #311).
+* `scripts/check-ts-allowlist.deno.js` — the compiled artifact the
+  governance workflow runs.
+* `scripts/check-ts-allowlist.ts` — the Deno archetype, retained as the
+  regression-suite target (`scripts/tests/check-ts-allowlist-test.sh`)
+  and for parallel-validation during the TS→AS dual-target window.
 * `hyperpolymath/standards#????` — proposal that landed this consumer.
 * `hyperpolymath/hypatia` — the scanner that emits findings.