chore: release v0.4.0

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

chore: release v0.3.1

Co-Authored-By: Claude Opus 4 <noreply@anthropic.com>

fix: add CGO_ENABLED=0 and docker smoke test to CI

The CI build was missing CGO_ENABLED=0, producing dynamically-linked
binaries that fail in the scratch image (no libc/dynamic linker).

Also add a smoke test step that runs `docker run --version` before
pushing, so broken images never reach the registry.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Merge CI and release workflows into single workflow

The two workflows were nearly identical — same test/build/docker jobs
duplicated across ci.yml and release.yml. Now one workflow handles all
three triggers (push, PR, release) with conditional steps:

- Version ldflags: baked in on release, omitted otherwise
- Release upload: only on release events
- Docker tags: semver on release, sha on push, latest on both
- Coverage: only on push to main

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Initial release: GitHub Copilot to OpenAI/Anthropic API proxy

Lightweight Go proxy that exposes GitHub Copilot as both OpenAI-compatible
and Anthropic-compatible API endpoints. Features include:

- OpenAI API: /v1/chat/completions, /v1/models, /v1/embeddings, /v1/responses
- Anthropic API: /v1/messages with smart routing (native, responses, chat completions)
- Full SSE streaming support for both formats
- GitHub Device Flow OAuth with automatic token refresh
- Zero third-party runtime dependencies (only golang.org/x/sync)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>