Docs: improve bilingual adoption entrypoint

[postmunnet]

Summary

Rewrite the public documentation entrypoint around the core adoption message:

AI agents can claim work is done. Trinity makes them prove it.

This keeps the architecture intact, but moves first-touch documentation from internal ritual/microkernel language toward evidence-driven AI work.

Changes

• Rewrite README.md as a bilingual, pain-first entrypoint
• Add WHY_TRINITY.md and WHY_TRINITY_TH.md
• Add Thai version lineage page and clarify the three version lines
• Move ritual commands below problem / example / quickstart context
• Add behavioral proof categories instead of relying only on test count
• Update Blueprint MCP stance to CLI-first, MCP-optional
• Add Tool Contract v1.0 freeze-candidate checklist without claiming stable API prematurely
• Update spec index FAQ to remove stale MCP lock-in rationale

Verification

Source checkout:

python3 -m pytest .ai/cli/tests -q

1862 passed, 6 skipped

Clean branch from current main:

python3 -m pytest .ai/cli/tests -q

1860 passed, 8 skipped

GitHub Actions CI:

PASS — CI run #22 on head dbade304bbda486df7169b89e9e017afa2ea1c37