Fleet v2: reusable review shim + config alignment

[jlocke2]

Converts this repo's Claude review workflow to a thin shim over the org-wide reusable workflow (PipelineDeals/pipeline_deals/.github/workflows/claude-review-reusable.yml).

• Reusable review shim: the shim owns only triggers, concurrency, and the repo-specific prompt. Review logic, caps, and generic guidance live in the reusable, so fleet-wide fixes become one PR to pipeline_deals while this repo keeps its own prompt.
• Prompt rewritten for a library: the old prompt reviewed a phantom Rails app (account_id scoping, N+1/index checks, Sidekiq job checklists, none of which apply to a DB-less packaged gem). The new prompt covers bugs, public-API compatibility for gem consumers, thread safety, gemspec/dependency hygiene, and conventions per AGENTS.md.
• AGENTS.md header: fixed the # CLAUDE.md heading left over from the rename.
• Read-deny alignment: extended permissions.deny in .claude/settings.json so Read is blocked for the same secret-file patterns the guard hook already Edit-blocks.

🤖 Generated with Claude Code

[sevgibson]

Approving — mechanical Fleet v2 consolidation, verified against the #18519 reusable pattern (which is merged, so the @master reference resolves). .claude/settings.json change is additive secret-deny hardening (nothing loosened); claude-review.yml becomes a thin shim -> reusable@master with synchronize/concurrency/statuses:write and the repo-specific prompt preserved; AGENTS.md header rename. Low risk.