feat: add CodeBuddy agent support

[studyzy]

Description

Adds CodeBuddy as a launchable coding agent alongside Claude Code, Codex, and OpenCode. edgee launch codebuddy starts a local Edgee gateway and routes CodeBuddy's traffic through it via the CODEBUDDY_BASE_URL env var.

Motivation

CodeBuddy is an Anthropic Messages API-compatible coding agent. The local-gateway flow lets Edgee apply its tool-output compression to CodeBuddy sessions, matching what's already available for Claude Code / Codex / OpenCode. The implementation mirrors the headroom project's codebuddy provider.

Changes

• New launch subcommand: edgee launch codebuddy (local-gateway only). Sets CODEBUDDY_BASE_URL to the local gateway address so CodeBuddy's /v1/messages requests flow through Edgee's compression pipeline.
• Provider registration:
  • config.rs: added codebuddy field to Profile.
  • auth/login.rs: added codebuddy to agent_label, coding_assistant_name, provider_config_mut, provider_config.
  • settings.rs: added codebuddy to PROVIDERS (routing not enabled, same as opencode).
  • alias.rs: added Codebuddy variant to Agent enum + CODEBUDDY_ALIAS spec; edgee alias now installs a codebuddy shim too.
• Statusline: reuses Claude's ensure_first_run_installed() on first launch (consistent with codex/opencode).
• Docs: updated README (quickstart, alias section, supported-setups matrix), CLAUDE.md, doc/architecture.md, and the compression-layer / gateway-core crate READMEs.

Hosted mode is intentionally not supported yet — there's no documented way to inject Edgee's x-edgee-api-key / x-edgee-session-id headers into CodeBuddy's outbound requests. Only the --local-gateway flow is wired up.

Testing

• cargo fmt --all -- --check passes
• cargo clippy --workspace -- -D warnings passes (no issues)
• cargo test --all passes (578 passed, 0 failed)
• New unit-test assertions for codebuddy in auth/login.rs and alias.rs
• cargo check passes

Checklist

• Code follows project style guidelines (gofmt-equivalent: cargo fmt)
• Self-reviewed the code
• Added tests for new functionality
• Updated documentation
• CI checks pass locally