refactor(translate): register translators per agent

[Stephen Belanger (Qard)]

Summary

Based on main now that #138 has merged.

Registry::default_agents() built each translator factory by hand. Source aliases went through canonical_source_name plus a second hardcoded allowlist in Registry::canonical_source, which duplicated the agent identities. With this PR:

• Agents are their own factories. TranslatorFactory now has Agent as its supertrait and no source method. Each agent type implements it directly in its translator module and registers itself alongside its other capabilities, and the registry keys factories by identity().source. The seven per-agent *TranslatorFactory structs are gone, and so is the intermediate Translate trait:

  pub(crate) trait TranslatorFactory: Agent {
      fn create(&self, session_id: &str) -> Box<dyn AgentTranslator>;
  }

• Registry construction. Registry::default_agents() registers every agent that registered a translator, plus the debug translator, as before. The debug translator has its own debug identity but isn't in the agent registry, since it isn't a coding agent.

• Public API. Agent is crate-private, so TranslatorFactory is too. It and the unused Registry::register are no longer exported. Nothing outside the crate implemented the trait or registered factories; the bt CLI doesn't use either.

• Shared Git metadata cache. The cache is now process-wide instead of one per registry. That's safe because repository entries are revalidated against the git directory before reuse and "not a repository" results expire. A daemon already uses a single registry, so in practice only tests and imports in the same process now share it.

• Alias resolution. canonical_source_name and Registry::canonical_source now resolve names through the agents' identities. Accepted names are each agent's id, its hook source, and its aliases, plus debug. Factories that a host registers under any other name are still rejected, as before.

Behaviour

None. The registered sources, the accepted aliases (claude → claude-code, open-code → opencode) and the rejection of unknown sources are unchanged. Two new tests pin them.

Testing

• cargo clippy --all-features --all-targets -D warnings is clean.
• cargo test --all-features --no-fail-fast: everything passes except trace_runtime::tests::doctor_reports_a_daemon_that_{cannot_authenticate_the_route,resolves_other_credentials}, which fail the same way on main in my local environment.

🤖 Generated with Claude Code

[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 2026-10-06T12:39:56.368160Z	caadc9e	PR opened

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "Codex (@codex) review" or "Codex (@codex) security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.