fix: sign macOS builds and harden team runtime

[terisuke]

Summary

• sign compiled darwin binaries with Bun's recommended macOS entitlements before smoke testing
• sanitize preview channels and version strings derived from branch names
• make team/background use the session directory for state when no git worktree is available
• detach background workers from the parent turn abort signal and cover the regressions in team plugin tests

Verification

• bun run build
• bun run typecheck
• bun test test/plugin/team.test.ts
• bun test test/agent/agent.test.ts
• bun test test/plugin/trigger.test.ts
• bun test test/session/prompt-effect.test.ts
• bun test test/session/processor-effect.test.ts
• bun test test/session/snapshot-tool-race.test.ts
• installed binary checks via opencode run/serve with real team/background workflows

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[Copilot]

Pull request overview

This PR improves release/build hygiene and guardrails runtime robustness by (1) signing macOS CLI binaries before smoke tests, (2) sanitizing channel strings derived from env/branch names, and (3) hardening the team/background tools to behave better when no git worktree is available, with regression tests.

Changes:

• Add channel sanitization for OPENCODE_CHANNEL and git branch --show-current.
• Sign darwin binaries during the build pipeline using Bun-recommended macOS entitlements.
• Update team plugin state storage/root selection and detach background workers from the parent abort signal; add new tests covering the regressions.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
packages/script/src/index.ts	Sanitizes preview channel values used to derive preview versions.
packages/opencode/script/build.ts	Adds macOS codesigning step (entitlements + ad-hoc signing) before smoke tests.
packages/guardrails/profile/plugins/team.ts	Uses a project root fallback when worktree is unavailable; detaches background abort; gates worktree isolation.
packages/opencode/test/plugin/team.test.ts	Adds regression tests for non-git state root and detached background abort behavior.

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