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.

.opencode/agent/dev.md

@@ -10,7 +10,7 @@ git worktree and branch. Never check out, rebase onto, or push to `main`. Confir
 the worktree root and branch before you edit. Use only paths under that root.
 
 Do only the assigned scope. Note anything outside that scope in one line and do not
-investigate it further. Use `bridge_ask{question}` only when a decision belongs to
+investigate it further. Use `fleet_ask{question}` only when a decision belongs to
 the lead, such as an unclear requirement or two defensible fixes. Do not ask about
 something you can decide by reading more code.