fix(copilot): route enterprise Copilot seats to the right endpoint and host

[Bhasvanth-Dev9380]

The bug

A GitHub Copilot Business/Enterprise login failed every turn with 421 Misdirected Request, whatever the prompt was.

An enterprise seat's /models list carries ids Pi's bundled catalog doesn't have yet (the gpt-5.6-* family). The never-miss resolver synthesizes an unknown id by cloning a catalogued model of the same provider — but it cloned the first one, claude-fable-5, an openai-completions entry. Copilot serves GPT-5+/codex only on /responses, so every request went to /chat/completions and the edge answered 421.

Two aggravating factors on the same path:

• the bundled catalog hardcodes api.individual.githubcopilot.com, but a business/enterprise token must use its own host (encoded in the token's proxy-ep);
• 421 classified as unknown — transient — so the loop burned three identical retries and surfaced last reason=unknown.

The approach

GitHub advertises no endpoint metadata in /models (github/copilot-cli#4337), so endpoint selection resolves newest evidence first:

1. learned — what the live API actually accepted for this id
2. advertised — an endpoint list on the account's own /models entry, parsed defensively so it activates itself if GitHub ever ships the field
3. family — the id-family rule, which is what Pi's catalog encodes and what GitHub's own clients assume

Changes

• new github-copilot-transport.ts — endpoint + host + editor-header correction, applied at one choke point in the agent loop so the catalogued and synthesized paths are both covered
• self-healing stream wrapper — an endpoint rejection before any event is emitted re-issues once on the other surface and is remembered, so a model family shipped after this release routes itself. Bounded to Copilot, once per stream, never after partial output
• host derived from the live token's proxy-ep, covering individual/business/enterprise and the GHE copilot-proxy. → copilot-api. shape; a deliberately configured gateway baseUrl is left alone
• synthesized Copilot ids take context window + vision from the account's own catalog instead of a template's
• template selection is family-matched for every provider: gpt-5.6-sol clones gpt-5.5, not the provider's first-listed model
• 421 and "not accessible via the /… endpoint" classify as model_not_found: one fast failure with an actionable message, and the fallback chain gets its turn

Verification

• npm run build clean; tsc --noEmit clean on both configs
• 708 agents + integrations tests pass, 21 of them new (github-copilot-routing.test.ts, plus 6 classifier cases)
• covered: endpoint rule per family, host derivation incl. GHE, family-matched templates, the heal wrapper (re-issue + learn, rethrow on unrelated errors, never replay after partial output, pass-through for other providers)

References

• gpt-5.6-luna advertised in /models but not accessible via /chat/completions (breaks MoA/aggregator tooling) github/copilot-cli#4337 — gpt-5.6-luna listed in /models, rejected on /chat/completions
• [Bug]: github-copilot/gpt-5.2-codex fails with 421 Misdirected Request (Responses API routing) openclaw/openclaw#8366 — GPT-5 models need the Responses API
• [Bug]: GitHub Copilot Enterprise accounts fail with HTTP 421 Misdirected Request openclaw/openclaw#1797 — Enterprise 421 on missing editor headers
• Copilot Business/Enterprise users can't use OpenCode — three compounding auth/endpoint/header issues anomalyco/opencode#20759 — business/enterprise host routing