docs(truth): S1 truth maintenance — CHANGELOG, stack line, MCP claim, conflict semantics, 90% cut-list

Findings 4-7 from the 2026-07-02 status analysis, per the session plan (S1):
- CHANGELOG rewritten truthfully (was: 'Plan phase - no framework code yet')
- README stack line names the split GA packages, not the agent-framework meta-package
- CLAUDE.md: MCP downgraded to extension point (in-process FunctionTool is the default seam)
- Verdict conflict semantics documented as chosen (store first-write-wins per id,
  disk/wiki last-write-wins per file; full B10 taxonomy deliberately deferred)
- docs/extending.md: explicit 90%-principle cut-list (B10, B11, U12, U14, concurrent fan-out)
- .gitignore covers .trekexecute-progress-* (docs/.DS_Store was already untracked/ignored -
  the plan's git rm --cached assumption was stale; no-op)

No code behavior changed (docstring only in verdicts.py). Suite 152/4 green, mypy clean,
ruff format --check clean.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AaQCFnfsh3tfq1VfzdJpoi

CLAUDE.md

@@ -13,7 +13,7 @@ Python ≥3.10. MAF (`agent-framework-core` 1.9.0). Pakkehåndtering: `uv`. To b
 - `ruff` for lint+format. `pytest` for test.
 - Modell-valg som konfig (modell-map rolle→Foundry-deployment), ikke spredt i kode.
 - Metode kodifiseres som **Agent Skill** (`agentskills.io`: `SKILL.md` + `scripts/` + `references/`).
-- Datatilgang via **MCP**-servere; data-source-konfig JSON-Schema-validert, fail-fast.
+- Datatilgang: in-process `FunctionTool` er default-sømmen i kjørestien; **MCP er extension point**, demonstrert via `build_mcp_server` (`datasource.py`) men ikke wiret inn i kjørestien. Data-source-konfig JSON-Schema-validert, fail-fast.
 
 ## Kommandoer
 - Sync: `uv sync`