fix(claude-intercept): require per-install auth for local CONNECT proxy

[luvs01]

Motivation

• Close a local-auth bypass where an unauthenticated loopback CONNECT + TLS path allowed callers to reach routed models and consume stored provider credentials without an OpenCodex admission key.
• Ensure the Claude intercept pair is safe by binding authorization to the CONNECT client rather than inferring trust from loopback location alone.

Description

• Add a per-install cryptographically-random proxy token with owner-only storage and accessor ensureClaudeInterceptProxyToken (src/claude/intercept/proxy-auth.ts).
• Require HTTP Basic proxy authentication on CONNECT requests and verify it in constant time before accepting a tunnel, returning 407 on missing/invalid credentials (src/claude/intercept/connect-proxy.ts).
• Wire the token into startup and client settings so managed Claude Code HTTPS_PROXY URLs carry the credential, and create the token on-demand when starting the intercept pair (src/claude/intercept/runtime.ts, src/claude/desktop-first-party.ts, src/claude/intercept/settings.ts).
• Harden the managed settings.json write path to owner-only mode (0600) and preserve migration behavior for legacy unauthenticated proxy URLs; update tests and architecture docs to reflect the authenticated transport contract (tests and structure/* edits).

Testing

• Ran the focused intercept tests with bun test tests/claude-integration/claude-intercept-proxy.test.ts and bun test tests/claude-integration/claude-intercept-settings.test.ts, both passing.
• Ran the integration scenario bun test tests/server/claude-intercept-integration.test.ts which passed with the authenticated proxy in place.
• Ran bun run typecheck, bun run structure:check, and bun run privacy:scan, all of which succeeded.
• Ran the full test suite with bun run test and observed a green run for the executed suite.

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Codex Task

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-21T01:30:58.943387Z	5adfffb	PR opened

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