fix(agent-mode): support current Codex ACP modes

[logancyang]

Summary

• map Codex's canonical Default, Plan, and Auto choices from the live ACP mode inventory
• support both the current agent / agent-full-access IDs and the legacy auto / full-access IDs
• deliver Copilot's composed prompt and startup safety defaults through CODEX_CONFIG for current adapters while retaining legacy -c arguments
• preserve unrelated user Codex config keys and reject malformed/non-object JSON clearly
• prefer a genuine native plan mode when one is advertised
• initialize current codex-acp sessions in agent mode while preserving user mode overrides
• update the non-Windows install command to @agentclientprotocol/codex-acp
• document Agent Mode's operating-mode picker

Root cause

The Codex descriptor hard-coded the legacy Zed adapter's native mode IDs. Current @agentclientprotocol/codex-acp releases advertise read-only, agent, and agent-full-access. The shared translator filters canonical modes against that inventory, so read-only was the only matching ID and Plan became the only visible picker option.

The current adapter also ignores arbitrary argv in ACP server mode and reads Codex session config from CODEX_CONFIG. Without the dual config transport, switching the recommended install package would drop Copilot's prompt wiring.

User impact

Codex users can switch among Default, Plan, and Auto again instead of becoming trapped in Plan. Copilot's Obsidian framing, custom prompt, and pill syntax reach both current and legacy adapter families. Existing installations using the legacy adapter retain their prior behavior.

Validation

• npm test -- --runInBand src/agentMode/backends/codex/CodexBackend.test.ts src/agentMode/backends/codex/codexModeMapping.test.ts src/agentMode/session/translateBackendState.test.ts — 66 tests passed
• npm run build — passed
• focused Prettier and ESLint plus staged pre-commit checks — passed
• isolated live plugin reload in logan-dev-vault — no uncaught errors or error-console entries
• full npm run lint remains blocked in the existing eslint-plugin-obsidianmd package.json flat-config path before project source is analyzed

Fixes logancyang/obsidian-copilot-preview#212

[chatgpt-codex-connector]

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