CB-622: rename bridge_* tool names to fleet_* in Markdown docs

Rename the eleven MCP tool names (bridge_ack/ask/list/poll/profiles/reply/
send/spawn/status/stop/whoami) to their fleet_* names across the Markdown
documentation. fleet_* is written as the normal name; one deprecation note
in README.md says bridge_* still works for one release.

docs/MCP-Contract.md is renamed only inside section 6 (lines 210-293):
sections 1-5 and 7-11 are stale pre-build design text (CB-609) and are
deliberately left with old names so dead text does not look maintained.

Also renames e2e/bridge_ask_transcript.md to e2e/fleet_ask_transcript.md
to match its content. CLAUDE.md, wiki/, plugin/skills/setup/SKILL.md and
.claude/skills/port-to-opencode/SKILL.md are owned by other units and are
untouched.

docs/CB-301-ext-Worktree-Provisioning.md

@@ -3,7 +3,7 @@
 **Status:** ✅ shipped — implemented at commit `97ecc71` (per-worker git worktree + config-parity
 overlay). As-built: `session/GitWorktrees.java` behind the `Worktrees` port, wired in
 `Bridged.main` and configurable via `worktreeRoot` / per-profile `parityOverlay`
-(see `bridged.example.yaml`). Branch/worktree surface in `bridge_list` landed with CB-304
+(see `bridged.example.yaml`). Branch/worktree surface in `fleet_list` landed with CB-304
 (`9fe04bf`); the worker-opened-PR checkpoint landed as CB-302 (`64e70ef`).
 **Extends:** [CB-301 Session Manager](CB-301-Session-Manager.md) (shipped, commit `54d907c`).
 **Realizes:** the config-parity requirement in [Worker Git Workflow](Worker-Git-Workflow.md).
@@ -122,7 +122,7 @@ public void release(String paneId) {
 
 ### Surface: MCP + REST
 
-- `bridge_spawn` gains an optional `worktree` arg: `true`, or a ticket slug string. Truthy ⇒ build a
+- `fleet_spawn` gains an optional `worktree` arg: `true`, or a ticket slug string. Truthy ⇒ build a
   `WorktreeRequest(slug, null)` and call the 5-arg `acquire`.
 - `POST /workers` gains `worktree` (+ optional `ticket`) in the body/query, same mapping.
 - `workerView`/`view(WorkerSession)` include `worktree` and `branch` **when non-null** (omit for