docs(adapters): codex adapter docs reflect the tiered install

[Steve-too]

Summary

Three doc surfaces went stale after the codex T2 work landed (PR #406 / issue #385).

Changes

• adapters/README.md — codex table row now lists both shipped tiers (config.toml + AGENTS.md)
• adapters/codex/README.md — rewritten: installer-first flow, per-tier summary, manual fallback preserved
• docs/getting-started.md — codex shown alongside claude-code in the mcp add and install-mcp sections

Acceptance criteria (from #390)

• Adapters table row for codex lists the shipped tiers accurately
• adapters/codex/README.md covers installer-first flow, per-tier summary, and the manual fallback
• getting-started shows the codex install alongside claude-code
• No stale references to the old copy-only behavior

Closes #390

Summary by CodeRabbit

• Documentation
  • Updated Codex adapter setup docs with a more explicit quick-start flow, including vouch install-mcp codex, project-local .codex/config.toml, and AGENTS.md snippet behavior (including rerun/idempotent updates) plus a restart reminder.
  • Clarified MCP configuration options for Codex, including guidance to edit either ~/.codex/config.toml or the preferred project-local configuration.
  • Expanded “Wire an agent” instructions to cover both Claude Code and Codex, with agent-specific install and verification commands and updated configuration snippet placement guidance.

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📥 Commits

Reviewing files that changed from the base of the PR and between 905930d and 13853fd.

📒 Files selected for processing (1)

• adapters/codex/README.md

✅ Files skipped from review due to trivial changes (1)

• adapters/codex/README.md

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📝 Walkthrough

Walkthrough

Documentation updates describe the tiered Codex MCP install flow: the adapters README table entry now references .codex/config.toml and AGENTS.md, the Codex adapter README adds installer-first quick start and tier explanations, and getting-started.md adds Codex-specific wiring instructions alongside Claude Code.

Changes

Codex documentation updates

Layer / File(s)	Summary
Codex adapter README tiered install flow adapters/codex/README.md	Quick start now leads with vouch install-mcp codex, explains T1 (.codex/config.toml) and T2 (AGENTS.md) tiers with idempotent rerun behavior, and documents project-local config as the preferred manual fallback over ~/.codex/config.toml.
Adapters README table entry update adapters/README.md	Table row for the codex adapter now lists .codex/config.toml and an AGENTS.md snippet instead of a single config.toml snippet.
Getting started wiring instructions for Codex and Claude Code docs/getting-started.md	“Wire an agent” section adds separate MCP registration examples for Claude Code and Codex, updated VOUCH_AGENT guidance, corresponding mcp list confirmation commands, and vouch install-mcp <host> references.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Possibly related issues

• feat(adapters): codex integration — bring the codex adapter to claude-code parity (tracking) #391: Codex adapter docs update for the T2 AGENTS.md snippet and tiered install flow matches this issue's Codex parity docs.
• feat(adapters): codex T2 — AGENTS.md fenced snippet #385: Documents the same T2 AGENTS.md fenced snippet feature described in this issue.

Possibly related PRs

• vouchdev/vouch#295: Both PRs modify the “Wire an agent” MCP wiring instructions in docs/getting-started.md.
• vouchdev/vouch#337: Also updates the “Wire an agent” section of docs/getting-started.md with Codex and Claude Code setup details.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	Title is concise and matches the main change: updating Codex adapter docs for the tiered install.
Linked Issues check	✅ Passed	The docs updates cover the adapter row, installer-first Codex README flow, and getting-started Codex integration, matching #390's core requirements.
Out of Scope Changes check	✅ Passed	The changes are limited to the three documentation surfaces called out in #390, with no obvious unrelated additions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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• Create PR with unit tests

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Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@adapters/codex/README.md`:
- Around line 31-32: The rerun behavior described in the README is inaccurate
for install(): it currently skips an existing fenced AGENTS.md block rather than
replacing it. Update the wording in the relevant README section to reflect the
actual behavior, or, if replacement is intended, adjust install() and its
fence-handling logic so reruns replace the existing snippet instead of leaving
it untouched.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 456a1a8c-c81b-4562-95c5-7adbc7c0cca5

📥 Commits

Reviewing files that changed from the base of the PR and between 36f035e and 905930d.

📒 Files selected for processing (3)

• adapters/README.md
• adapters/codex/README.md
• docs/getting-started.md