feat(server): Add the Builder persona prompt

[bryantderosier]

What does this implement or fix?

Adds the versioned Builder V1 operating contract and composes it through the Codex developer-instruction and Claude system-prompt channels. Runtime policy remains the authority boundary, while focused coverage ensures non-Builder launches stay unchanged and Builder cannot cross commit or push boundaries.

This is PR 7 of 10 in GitHub stack pingdotgg#120. It targets feature/agent-persona-integrity and depends on #81.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)
• This change requires a documentation update

How has this been tested?

The focused remaining-stack suite passed 234 tests across 10 files, including Builder prompt, runtime policy, Codex adapter, and Claude adapter coverage.

• Focused tests pass locally
• Existing behavior outside this layer remains covered
• The branch diff passes git diff --check

Screenshots or GIFs (Optional)

Not applicable to this server prompt and policy layer.

Merge order

This PR is part of GitHub stack pingdotgg#120. Merge from bottom to top:

#75 -> #76 -> #78 -> #79 -> #80 -> #81 -> #83 -> #82 -> #85 -> #118

Stack rebuilt 2026-09-09 (stack pingdotgg#120): #84 and #86 were dropped, and fork-boundary refactors moved the persona RPCs, guards, and client wiring into J5-owned files. Review threads were preserved.

Generated with GPT-5 using the Codex desktop app.

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