v2.0.0

The v2.0 stability lock. No new capability ships in 2.0 itself; everything new
since v1.9.0 shipped and was validated across the v1.9.x bridge. 2.0 locks the
JSON schema as the v2.0 contract, turns the Bayesian fusion layer on by default,
and ratifies the accumulated work.

Schema lock (G1)

• docs/recon-schema.json is bumped from "Stable v1.0 contract" to "Stable v2.0
  contract"; additive changes stay non-breaking within 2.x. The locked surface
  is the post-schema-hardening shape (SH1 to SH9): the slug_confidences object
  map, named wildcard_sibling_clusters objects, the fusion_enabled /
  record_type / schema_version discriminators, machine-readable error_kind,
  and the --include-ecosystem always-wrapper. Both schema copies stay
  byte-identical.
• recon doctor's first line now reads "v2.0 stable schema".

Fusion on by default (G2)

• The Bayesian inference layer runs on every lookup; it was opt-in behind
  --fusion through v1.9.x. --json always emits posterior_observations and
  slug_confidences, and fusion_enabled disambiguates the opt-out case. The
  computation costs no extra network calls.
• --no-fusion (new) opts out, reverting to the rule-based shape (empty fusion
  arrays, fusion_enabled: false). --fusion is kept as a now-default no-op for
  compatibility.
• The default panel stays clean: it renders the deterministic verdict as before
  and does not dump the credible interval. The panel "speak up when the layers
  disagree" refinement (surface the interval inline and demote the confidence dot
  on sparse or disagreement cases) lands as a 2.0.1 fast-follow.

Validation baseline

• Locked against a full-corpus fusion re-run (5238 successful domains, post-CAL14
  build): 100% deterministic-vs-Bayesian consistency (13560 of 13560
  high-confidence firings, zero disagreements), the CAL14 declarative
  email-policy behavior confirmed on real input, and zero cross-source conflicts.
  See validation/v2.0-corpus-run.md.

The migration guide is docs/migration-v2.md; the full validation trail and the
lock-ceremony record are under validation/.