feat(oab-mcp): fleet-aware tool surface — target by fleet name, scope to members (Part B slice 1)

[brettchien]

Drafted by Orca (ecs-claude) — flagging authorship (shared GitHub identity).

Slice 1 of the reverse-MCP client ADR (#36), and the completion of Part A on the MCP side. Tools took only cluster, so they could not name a fleet when two fleets share a cluster (orca + mira on oab) — deploy_list({cluster:"oab"}) returned both. This makes the MCP surface fleet-aware, the precondition for the single-oab-server design (D1).

What

• fleet arg on all 8 cluster-bearing tools (list/get/states/events/apply/scale/delete/runtime_context). A new target() resolver maps fleet (name) → the fleet's cluster (→ managing credential) + its member scope.
  • Unknown fleet → error, never a silent fall-through to the default cluster (that silent fallback is the AccessDenied class of bug the fleet work exists to kill).
  • No fleet → unchanged (cluster arg / server default). Back-compat.
• Listing (deploy_list, get_agent_states) filters results to the fleet's members.
• Writes (deploy_scale, deploy_delete) refuse a service outside the named fleet's members — a fleet handle only operates its own members (no-op for unscoped / whole-cluster calls).
• runtime_context reports the named fleet's binding, so two fleets on one cluster resolve distinctly.
• Membership match centralized in studio-cp FleetBinding::includes (full ECS name or short name; empty members ⇒ whole cluster), with unit tests.

Scope note

Credential stays cluster/account-granular (Part A): a fleet changes which members are seen/acted on and which binding is reported — not the auth identity. Two fleets sharing a cluster share one credential; cross-account per-fleet credentials are fleet ADR §5 Q4 (future).

Verification

• cargo check --all-targets clean for oab-mcp + studio-cp (full aws-sdk compiled).
• New studio-cp unit tests for includes (full name / short name / non-member / empty=whole-cluster).
• ⚠️ Test execution left to CI (cargo test --workspace): the test-profile codegen of aws-sdk-ec2 OOMs the authoring box — the exact constraint ci.yml documents. The build-test + smoke gate exercises it.

🤖 Generated with Claude Code