chore(voyage): S34 — V30 economy-profile self-declares experimental (uncalibrated Jaccard floor)

The economy profile's cross-tier Jaccard floor (0.55) rests on parked-synthetic
fixtures; empirical Step-17 calibration is v4.2-budget-gated ($60–120,
unauthorized). Fork resolved as label-not-calibrate: the experimental status,
previously prose-only in docs/profiles.md, now lives in the profile data and is
machine-checked. No new user-facing capability — honest labeling + a guard.

- lib/profiles/economy.yaml: add `experimental: true` (with rationale comment).
- lib/validators/profile-validator.mjs: recognize `experimental` as an OPTIONAL
  boolean; non-boolean → PROFILE_INVALID_ENUM. Absent ⇒ tier is stable
  (premium/balanced unaffected, profile_version stays 1.0 — additive).
- README.md + docs/operations.md + docs/profiles.md: flag the `economy` table
  row "⚠ Experimental (uncalibrated Jaccard floor)".
- tests/synthetic/profile-jaccard-calibration.md + analysis §6/§10 + backlog
  plan §S34: cross-reference the marker; mark V30/S34 done.

+5 tests (739 → 744, 742/2/0): economy declares experimental:true; premium and
balanced do not; validator rejects non-boolean experimental; every profile-doc
economy row is flagged; the flag tracks the calibration's parked-synthetic
status (must drop in the same change that lands real calibration).

Closes the balance backlog (4/4, S31–S34). claude plugin validate green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LqBYc8Ltrk7LipyJmGxXiB

lib/profiles/economy.yaml

@@ -18,4 +18,9 @@ parallel_agents_min: 2
 parallel_agents_max: 3
 external_research_enabled: false
 brief_reviewer_iter_cap: 1
+# Experimental: the cross-tier Jaccard floor (0.55) rests on parked-synthetic
+# fixtures — empirical Step-17 calibration is deferred to v4.2. Drop this flag
+# in the SAME change that lands calibration (status: empirical). See
+# tests/synthetic/profile-jaccard-calibration.md and docs/profiles.md.
+experimental: true
 ---

lib/validators/profile-validator.mjs

@@ -9,6 +9,10 @@
 //   parallel_agents_max        : number (≥ parallel_agents_min)
 //   external_research_enabled  : boolean
 //   brief_reviewer_iter_cap    : number (≥ 1)
+//   experimental               : boolean (OPTIONAL) — true marks a tier whose
+//                                  gating constants are not yet empirically
+//                                  calibrated (e.g. economy's parked-synthetic
+//                                  cross-tier Jaccard floor). Absent ⇒ stable.
 //
 // Issue codes:
 //   PROFILE_MISSING_FIELD  — required top-level frontmatter field absent
@@ -99,6 +103,12 @@ export function validateProfileContent(text, opts = {}) {
       `brief_reviewer_iter_cap must be number (got ${typeof fm.brief_reviewer_iter_cap})`));
   }
 
+  // Optional field: `experimental` (boolean). Absent ⇒ tier is stable.
+  if ('experimental' in fm && typeof fm.experimental !== 'boolean') {
+    errors.push(issue('PROFILE_INVALID_ENUM',
+      `experimental must be boolean (got ${typeof fm.experimental})`));
+  }
+
   // phase_models validation
   if ('phase_models' in fm) {
     if (!Array.isArray(fm.phase_models)) {