Add Tool

A new tool touches four places. Do all four or the tool is half-registered.

1. src/tools/<name>.ts

• zod schemas for input and output.
• Declare both sideEffect (none|read|write|network|exec) and risk (low|medium|high|critical) on the schema. Be honest — these drive the permission classifier.
• All filesystem access goes through src/sandbox/fs.ts helpers.
• All shell commands go through src/sandbox/shell.ts + classifyCommandRisk.
• Request permission via requestPermission (src/permissions/manager.ts) before the side effect, not after.
• Return { ok: true, data } / { ok: false, error }. Throw only for programmer errors, and then use ForgeRuntimeError.

2. Registration

Wire it into the registry, following the pattern of an existing tool like src/tools/read-file.ts.

3. test/unit/<name>.test.ts

Minimum coverage:

• happy path with valid input,
• zod rejection on invalid input,
• permission denied → structured error (not throw),
• sandbox refuses path-escape,
• (if shell) critical command hard-blocked.

Use vi.mock for the permission manager and sandbox boundaries. No real filesystem writes outside os.tmpdir().

4. Docs

If user-visible, update the tools table in docs/ARCHITECTURE.md and the README "At a glance" count.

Finish with the verify skill.