P5: light-tier canary — gadfly-shaped reviewer on executus core

examples/reviewer proves the core is sufficient for a static-binary light host
(gadfly's shape) with NO batteries:
- config.Env + model.Configure  -> env-driven model fleet + tier overrides
- model.ParseModelForContext    -> tier resolution + failover
- fanout.Run (PerKey caps)      -> N models x M lenses swarm, per-provider bound
- model.GenerateWith[T]         -> structured findings per (model, lens) cell
- Consolidate                   -> one verdict-led report section per model

Hermetic test runs the full 2x3 swarm against majordomo's fake provider and
asserts the consolidated verdicts. A go list -deps CI check asserts the canary
imports ZERO batteries (the light-tier invariant) — gadfly's go.sum stays free
of gorm/redis/discordgo/sqlite. README + docs updated.

This is the canary; migrating the LIVE gadfly repo onto executus core is a
follow-up (kept separate to not destabilize the active reviewer).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -115,7 +115,7 @@ repackaging.
 
 P0 module + zero-coupling moves + core seams (this) → P1 tool registry + model →
 P2 run kernel + Ports inversion → P3 generic tools + defaults → P4 persona/skill
-redesign + batteries + SQLite store → P5 gadfly on core (light-tier canary) → P6
+redesign + batteries + SQLite store → P5 gadfly-on-core canary (examples/reviewer ✓) → P6
 rewire mort + tag v0.1.0. The mort-side rewrite reuses mort's existing
 `mort_*_adapters.go` wall as the host adapter layer.