feat: add declarative Outfit files for provider config

[outofcoffee]

Add an Outfit file: a flat, Dockerfile-style way to capture one opencode provider selection and apply it with a single command.

Summary

• Add the Outfit file format — PROVIDER / FAMILY / MODEL / CONTEXT / BASEURL instructions, one provider per file. Keywords are case-insensitive (UPPERCASE canonical), with # comments inline or full-line.
• CONTEXT and BASEURL map to the --context and --base-url flags (with URL / BASE-URL / BASE_URL aliases), so an Outfit can express everything oc-config add can.
• Add oc-config apply [path] to apply an Outfit, defaulting to ./Outfit so a bare oc-config apply works. It reuses the existing add pipeline via a shared applySelection, so config merges behave identically.
• Add oc-config export [-p name] to reconstruct an Outfit from the current config, naming a FAMILY when the configured models match one and otherwise the specific MODEL.
• Document the format in docs/outfit-file.md (end-user oriented) and move the llama.cpp guides under examples/, each now a directory with a README and a ready-to-apply Outfit.
• Cover the new code with tests for family matching, keyword parsing, and the export/apply edge cases; total coverage rises from 87.7% to 90.3%.

Implementation details

• An Outfit is deliberately a single-provider file with no indentation — it maps one-to-one onto an oc-config add, which kept the parser small and the apply path a thin wrapper over existing logic.
• export is a best-effort inverse of writeConfig: loadConfigState reads back each provider's model keys, options.baseURL, and per-model limit.context; matchFamily collapses a known model set to its family name. It records a BASEURL only when it overrides the catalogue default, and a CONTEXT only when the exported models agree on a single value, so it never invents or guesses data.
• Rebased onto the recently merged --base-url (feat: allow API base URL override via flag or env var #1) and --context (feat: add --context flag to set model context window #2) work; the Outfit keywords reuse those same selection fields and the example guides now set a matching context window in-file.