feat: UI fixes + boocontext remainders — Memory project selector, agent event toasts, codecontext→boocontext left-overs

Fixes 3 remaining UI items from the component-wiring audit:
  - Memory page: project selector dropdown (Item 1)
  - Agent events: collision_warning + agent_message toasts via sonner (Item 2)
  - Reasoning delta already wired and working (Item 3)

Also picks up uncommitted boocontext rename changes from the subagent batch:
  - synthesisPipeline.ts tier tool names updated
  - tiers.ts STANDARD_TOOL_NAMES clears old codecontext tools
  - tool-utils.ts BUILT_IN_TOOLS updated
  - .env.example / README.md reference boocontext MCP
  - ROADMAP.md boocontext entry
  - codecontext/ dir + docs/codecontext-ts-plan.md removed (already gone from tree)

.codesight/graph.md

@@ -12,8 +12,6 @@
 - `apps/coder/src/services/agent-backend.ts` — imported by **14** files
 - `apps/coder/src/services/acp-tool-snapshot.ts` — imported by **14** files
 - `apps/server/src/config.ts` — imported by **14** files
-- `apps/server/src/services/tools/codecontext/factory.ts` — imported by **14** files
-- `apps/server/src/services/tools/types.ts` — imported by **13** files
 - `conductor/src/types.ts` — imported by **13** files
 - `apps/coder/src/services/provider-config-registry.ts` — imported by **12** files
 - `apps/coder/src/config.ts` — imported by **11** files
@@ -22,6 +20,8 @@
 - `apps/server/src/services/agents.ts` — imported by **10** files
 - `apps/server/src/services/path_guard.ts` — imported by **10** files
 - `apps/coder/src/services/pending_changes.ts` — imported by **9** files
+- `apps/server/src/services/inference/payload.ts` — imported by **9** files
+- `apps/server/src/services/inference/dcp/messages.ts` — imported by **9** files
 
 ## Import Map (who imports what)