Add scout MCP server for browser recon + msgspec workspace dep

- tools/scout/: browser automation MCP server using Pydoll (CDP, no WebDriver)
  - scout_visit, scout_elements (text-first), scout_click, scout_fill, scout_select
  - scout_scroll, scout_text, scout_screenshot (opt-in)
  - scout_har_start / scout_har_stop (asyncio task holds recording context open)
  - scout_analyze: HAR parsing with HarEntry/HarSummary msgspec structs
  - Standalone project (not workspace member — websockets conflict with prefect)
  - Runs via: uv run --directory tools/scout scout-server

- .mcp.json: registers scout as Claude Code MCP server (project scope)

- msgspec>=0.19 added to root project deps (workspace-wide struct/validation)

- coding_philosophy.md: document msgspec as approved dep, usage rules

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

coding_philosophy.md

@@ -201,6 +201,13 @@ active_users = [u for u in users if u.is_active()]
 - Small, focused libraries
 - Direct solutions
 - Understanding what code does
+
+**Approved dependencies (earn their place):**
+- `msgspec` — struct types and validation at system boundaries (external APIs, user input,
+  inter-process data). Use `msgspec.Struct` instead of dataclasses when you need: fast
+  encode/decode, built-in validation, or typed containers for boundary data.
+  **Rule:** use Structs at boundaries (API responses, HAR entries, MCP tool I/O) —
+  keep internal plumbing as plain dicts/tuples.
 </question_dependencies>
 
 </architecture_principles>