docs(pstack): commit figure-it-out units, then open the PR

[jhonnyisaacc]

Why

A figure-it-out run verified six units and left them uncommitted on one branch. The agent then asked three times before opening a PR. Phase C now commits each verified unit before the next, and the run opens the PR at the end.

What changed

• Phase C commits each verified unit before the next unit starts.
• Phase E runs Opening a PR at the end of the run and does not ask permission.

Scope

• Covers when a figure-it-out unit is committed, and that the run opens its PR without a permission ask.
• Leaves how many PRs a change gets to Opening a PR. The Phase B line in docs(pstack): default to one PR per requested change #522 stays as it is.
• Leaves the plugin version alone.

Tradeoffs

The open-PR step is in Phase E so the Phase C loop commits a unit and does not open a PR per unit.

Blast Radius

Only agents running figure-it-out change behavior. They commit after each verified unit and open the PR without asking. No other skill text changes.

Verification

• node scripts/validate-plugins.mjs reports all plugins validated.
• Open PR docs(pstack): default to one PR per requested change #522 is the only other open PR that edits this file, and its hunk is Phase B, not Phase C or Phase E.