Add esper:revise skill for user-driven document revision

Context

Plan files, phase files, and fix documents are the backbone of the esper workflow — they define what gets built and how. Currently there is no structured way for a user to give feedback on these documents and have revisions applied. An esper:revise skill would let the user comment on a plan or phase doc, and the agent would apply the requested changes.

This is a user-driven workflow: the user provides the feedback, and the agent makes the edits. It is NOT an auto-review skill — the agent does not evaluate quality on its own.

Approach

1. Create skills/esper-revise/SKILL.md with the following workflow:

   • Step 1: Check setup — run esperkit config check, read .esper/CONSTITUTION.md
   • Step 2: Identify target — accept a plan ID, phase name, or file path as $ARGUMENTS. If no argument, use AskUserQuestion to ask which document to revise. Resolve to a file path (e.g. .esper/plans/pending/021-explore-skill.md or .esper/phases/phase-4.md)
   • Step 3: Read and present — read the target document and display it to the user for review
   • Step 4: Collect feedback — use AskUserQuestion to ask the user what they want to change. Accept free-form comments, specific section edits, or structural feedback. Allow multiple rounds of revision
   • Step 5: Apply revisions — edit the document according to the user's feedback. Show the changes made and ask if further revisions are needed
   • Step 6: Confirm — when the user is satisfied, confirm the document is updated and suggest next steps (/esper:apply to start building, /esper:backlog to review the queue)

2. No changes to bin/cli.js.

Files to change

• skills/esper-revise/SKILL.md (create — the skill definition)

Verification

• Run: node --test test/
• Expected: existing tests still pass
• Edge cases: handle missing or malformed frontmatter, plans that reference files that don't exist yet, and multiple rounds of user feedback

Progress

• Created skills/esper-revise/SKILL.md with 6-step workflow (check, identify target, read, collect feedback, apply revisions, confirm)
• Modified: skills/esper-revise/SKILL.md
• Verification: 64/64 tests pass