fix(agent-core): run bash with process cwd

[tt-a1i]

Summary

Fixes #850.

• run Bash commands with the process cwd instead of prefixing the shell source with cd '<cwd>' &&
• keep Windows Git Bash >nul rewriting, but leave cwd handling to the process runner
• normalize Git Bash-style /c/... cwd values back to Windows drive paths before spawning
• update Bash tests so they assert both the spawned argv and the cwd passed through withCwd()

Validation

• pnpm --filter @moonshot-ai/agent-core exec vitest run test/tools/bash.test.ts test/tools/shell-quoting.test.ts
• pnpm --filter @moonshot-ai/agent-core run test
• pnpm --filter @moonshot-ai/agent-core run typecheck
• pnpm exec oxlint --type-aware packages/agent-core/src/tools/builtin/shell/bash.ts packages/agent-core/test/tools/bash.test.ts packages/agent-core/test/tools/shell-quoting.test.ts --quiet
• pnpm --filter @moonshot-ai/agent-core run build
• git diff --check

AI Assistance Disclosure

I used Codex to review the changes, sanity-check the implementation against existing patterns, and help spot potential edge cases.

[changeset-bot]

🦋 Changeset detected

Latest commit: de1a877

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@moonshot-ai/kimi-code	Patch

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[tt-a1i]

I missed #851 when checking for existing work because the title did not include #850. Closing this as a duplicate.