feat(agent-manager): target existing managed worktrees

[marius-kilocode]

What Problem This Solves

Agent Manager orchestrators could create sessions only in the caller directory or in newly created worktrees. Review and follow-up sessions therefore could not target an existing managed worktree.

Why This Change Was Made

Add an explicit worktreeID start target resolved from action: "list". The target is scoped to the caller project and uses the existing local-session path.

User Impact

Fresh sessions can be started in an existing managed worktree without creating a branch, running setup, or deleting the target on failure. Existing requests without worktreeID keep their current behavior. Invalid, unknown, or foreign targets fail without fallback.

Evidence

Focused CLI and extension tests, package typechecks, extension compile, isolated VS Code self-test, and generated SDK validation passed.

Related to #13833.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (10 files)

• .changeset/managed-worktree-target.md
• packages/kilo-vscode/src/agent-manager/tool-start.ts
• packages/kilo-vscode/tests/unit/agent-manager-tool-project.test.ts
• packages/kilo-vscode/tests/unit/agent-manager-tool-start.test.ts
• packages/opencode/src/kilocode/agent-manager/event.ts
• packages/opencode/src/kilocode/tool/agent-manager.ts
• packages/opencode/src/kilocode/tool/agent-manager.txt
• packages/opencode/test/kilocode/agent-manager-tool.test.ts
• packages/sdk/js/src/v2/gen/types.gen.ts
• packages/sdk/openapi.json

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_{Reviewed by grok-4.6 · Input: 97.1K · Output: 19.6K · Cached: 1.1M}

_{Review guidance: REVIEW.md from base branch main}

[WebReflection]

I think concerns around != null instead of !== aren't adding anything to this PR so I'll approve, we should probably add automatically some linter exception when that's needed or have a broader utility that allows that comparison once:

// eslint-ignore-next or something similar
const isNullish = value => value == null;