docs(api-surfaces): document missing MCP tools (write, evolve, insights, tune)

[Souptik96]

Summary

docs/api-surfaces.md was out of sync with the MCP tool surface registered in
core-api/src/core_api/mcp_server.py. The charter named only 8 of the 12
registered MCP tools, so a reader inventorying the API surface from the doc
concluded there was no write, outcome-reporting, insights, or tuning tool —
while the server registers and serves all four.

This documents the four missing tools and gives the whole MCP surface a
first-class, per-tool reference.

Changes

• Add a new ## MCP tool surface section: a table of all 12 registered
  MCP tools with Transport(s), Trust required, and a one-line Contract,
  matching the issue's requested shape. Values are sourced from the ToolSpec
  single-source-of-truth in core-api/src/core_api/tools/*.py and the handlers
  in core_api/mcp_server.py.
• Name memclaw_write (bulk write) and memclaw_tune (per-agent search
  profile) in the existing Surface ownership table.
• Add the previously-absent Karpathy Loop concerns to the ownership table:
  Outcome reporting / weight reinforcement (memclaw_evolve) and
  Reflection / insights (memclaw_insights).

The four previously-undocumented tools

Tool	Trust	Contract
memclaw_write	0 (needs write capability)	Primary write path — single or batch (≤100).
memclaw_evolve	≥1 (agent), ≥2 (fleet/all)	Outcome reporting / weight reinforcement.
memclaw_insights	≥1 (agent), ≥2 (fleet/all)	Reflection (contradictions, failures, stale, divergence, patterns, discover).
memclaw_tune	0 (needs write capability)	Persistent recall-profile tuning.

Verification

• Cross-checked every row against the handler definitions in mcp_server.py
  and the ToolSpec declarations (trust levels, plugin_exposed,
  op/scope-specific floors).
• Confirmed REST counterparts exist for each tool (entities.py, agents.py,
  evolve.py, insights.py, stats.py, documents.py, keystones.py,
  memories.py).
• Docs-only change; no code paths touched.

Closes #550