feature: Add standing-order breadcrumb to Link Health Fixer PR bodies

[rubambiza]

Summary

Link Health Fixer PR bodies do not link back to the automation program or its standing order, so a reader on the target repo cannot navigate to what generated the PR or the governing policy. The Link Health Scanner already adds this breadcrumb footer to the issues/dashboard it posts; the fixer should do the same on the fix PRs it opens.

Current behavior

scripts/link-health-fixer.sh builds its PR body starting at line 517:

pr_body="Automated fix by OpenClaw Link Health Fixer.
Broken internal links updated to point to current file locations.

| File | Old Path | New Path |
|------|----------|----------|"

There is no link to the standing order or the source suite. Example of a fixer PR missing the breadcrumb: rossoctl/workload-harness#61.

Desired behavior

Mirror the scanner's footer. scripts/link-health-scanner.sh:536 already does:

Generated by the [Rossoctl Link Health Scanner](https://github.com/$SOURCE_REPO/blob/main/standing-orders/link-health.md).

Append an equivalent footer to the fixer's PR body, e.g.:

Generated by the [Rossoctl Link Health Fixer](https://github.com/$SOURCE_REPO/blob/main/standing-orders/link-health.md).

Why this is low-effort

• $SOURCE_REPO is already set and exported by load_org_profile (scripts/org.sh:140,146), defaulting to <org>/automation.
• The fixer already sources program-lib.sh (scripts/link-health-fixer.sh:11), so $SOURCE_REPO is in scope — no new plumbing needed.
• The change is a single appended line to the pr_body string (after the table loop that ends around line 528), matching an established pattern in a sibling script.

Acceptance

• Fixer PR bodies end with a "Generated by ... standing-orders/link-health.md" footer, linking via $SOURCE_REPO.
• Footer renders correctly (verify a dry-run or a real fixer PR body).

Assisted-By: Claude Code