fix(quota): isolate Forge runtime state

[nerdalert]

Summary

Follow-up to #123 that fully isolates Forge runtime state for each token-quota qualification run.

• Pass a run-specific --state-dir to Forge up, every stack apply, and down.
• Keep Forge-managed .forge/runtime/... template targets unchanged.
• Materialize only exec-command references to the corresponding run-specific state path.
• Remove the run-owned Forge state directory after successful teardown.
• Add regression coverage proving template targets and shell consumers resolve to the same isolated runtime files.

Why

The functional qualification in #123 passed all nine quota scenarios, but teardown loaded stale cluster names from the shared default .forge/state.json. Once state was isolated, Forge correctly wrote generated files under the new state directory, while topology exec steps still read the literal old .forge/runtime/... path.

This patch connects both sides of that boundary without returning to shared state or broad deletion.

Validation

• 23 focused token-quota tests passed.
• cargo clippy -p xtask --all-targets -- -D warnings passed.
• Nightly formatting and git diff --check passed.

The complete post-merge qualification matrix will exercise automatic teardown. No quota, routing, AI, Praxis, or Forge production source is changed.