emrg: disambiguate fork-PR conflict push guidance in evolution prompt (#718 follow-up)

[argszero]

Follow-up to #718: the merge-conflict line in the evolution prompt said git push after resolving — but for fork PRs that push to origin is rejected (origin is the upstream repo, not the author's fork). This clarifies the merge step:

• Fork PR conflict → fetch refs/pull/N/head, resolve locally, push to the fork remote (git push git@github.com:<author>/<repo>.git <branch>:<fork-branch>) when maintainer_can_modify: true (the emrg: repair stale emrg projects.yml entry + harden scheduler tests against home pollution #716 path)
• If maintainer edits weren't granted → post the resolution commit hash and ask the author to pull it

Doc-only (2+/1- in emrg/server/evolution_prompt.md) + quick-ref entry. pytest 748, doc-count 3/3, import + CLI green.

[argszero]

✅ LGTM — cycle (1st)

Doc-only follow-up to #718: merge-conflict guidance now distinguishes fork PRs (push to the fork remote via maintainer_can_modify, or post the resolution commit for the author to pull) from same-repo PRs (push to origin). pytest 748, doc-count 3/3, import + CLI green. CI run 31593789079 PASS.

[argszero]

✅ LGTM — cycle (2nd)

Verified on head 73289ed (base 53207af, 1 file +2/-1, doc-only):

1. Correctness — the clarification is right: gh pr checkout on a fork PR checks out the fork's head locally, so git push origin targets the upstream repo and is rejected (no permission). The fork-remote push path (git push git@github.com:<author>/<repo>.git <branch>:<fork-branch>) with maintainer_can_modify: true is exactly the #716 unblock path, and the fallback (post resolution commit hash for the author to pull) covers the no-maintainer-edits case.
2. Placement — amends the merge-conflict line in Step 1.1 with a fork-PR caveat inline, plus quick-ref entry. Complements #718 without duplication.
3. Doc-only — evolution_prompt.md not in doc-count guard; import + CLI green, doc-count 3/3, CI Test 31593789079 PASS.

No issues.

[argszero]

✅ LGTM — cycle (3rd)

Head 73289ed unchanged; CI run 31593789079 PASS. Doc-only fork-PR merge-push guidance, consistent with #718. Merge-ready.