docs: OPT_OUT_DEMAND_LOG.md — evidentiary base for governance decisions

Cycle #21 ships governance infrastructure, not implementation. Maintainership
mode means sometimes the right deliverable is a decision framework, not code.

Problem context:
OPT_OUT_AUDIT.md (cycle #18 bonus) established 'demand-backed audit' as the
next step. But without a structured way to record demand signals, 'demand-backed'
was just a slogan — the next audit cycle would have no evidence to work from.

This commit creates the evidentiary base:

New file: OPT_OUT_DEMAND_LOG.md
- Per-surface entries for all 12 OPT_OUT commands (Groups A/B/C)
- Current state: 0 signals across all surfaces (consistent with audit prediction)
- Signal entry template with required fields:
  - Source (who/what)
  - Use case (concrete orchestration problem)
  - Markdown-alternative-checked (why existing output insufficient)
  - Date
- Promotion thresholds:
  - 2+ independent signals for same surface → file promotion pinpoint
  - 1 signal + existing stable schema → file pinpoint for discussion
  - 0 signals → stays OPT_OUT (rationale preserved)

Decision framework for cycle #22 (audit close):
- If 0 signals total: move to PERMANENTLY_OPT_OUT, close audit
- If 1-2 signals: file individual promotion pinpoints with evidence
- If 3+ signals: reopen audit, question classification itself

Updated files:
- OPT_OUT_AUDIT.md: Added demand log reference in Related section
- CLAUDE.md: Added prerequisites for promotions (must have logged signals),
  added 'File a demand signal' workflow section

Philosophy:
'Prevent speculative expansion' — schema bloat protection discipline.
Every new CLAWABLE surface is a maintenance tax. Evidence requirement keeps
the protocol lean. OPT_OUT surfaces are intentionally not-clawable until
proven otherwise by external demand.

Operational impact:
Next cycles can now:
1. Watch for real claws hitting OPT_OUT surface limits
2. Log signals in structured format (no ad-hoc filing)
3. Run audit at cycle #22 with actual data, not speculation

No code changes. No test changes. Pure governance infrastructure.

Related: #18 cycle (OPT_OUT_AUDIT.md), maintainership phase transition.

OPT_OUT_AUDIT.md

@@ -144,6 +144,7 @@ If external claws report needing JSON from any OPT_OUT surface:
 
 ## Related
 
+- **OPT_OUT_DEMAND_LOG.md** — Active survey recording real demand signals (evidentiary base for any promotion decision)
 - **SCHEMAS.md** — Clawable surface contracts
 - **CLAUDE.md** — Development guidance
 - **test_cli_parity_audit.py** — Parametrized tests for CLAWABLE_SURFACES enforcement