Add a "Linked from" backlinks row to open notes

[AllTerrainDeveloper]

What this does

Notes can already link forward with [[label|note-id]], but there is no way to see which notes point at the one you are reading. This adds a Linked from row at the bottom of every open note, listing the notes that link to it, newest first. Each entry is clickable and opens the linking note.

How it works

• A scanner extracts wiki-link targets from note bodies using the same parsing rules as the renderer, so links inside fenced code blocks or inline backticks do not count.
• Targets resolve through resolveNote(), exactly like link clicks, so both [[title]] and [[label|note-id]] forms work and dead links are ignored.
• A note never lists itself.
• The row is bounded at 20 entries, with an "and N more" summary, matching the app's bounded-rendering approach.
• The index is rebuilt on each story render — no cache to invalidate, so it is always correct after saves and deletes.

Tests

• New Chrome scenario: creates a note with a real link, a code-quoted link, a dead link, and a self-link, then asserts the target shows exactly one backlink and that clicking it opens the source note.
• Static source check for Chrome-less runs.
• Full suite green: PIPLET_REQUIRE_CHROME=1 php tests/run.php → 433 assertions, plus the unsafe suite.

🤖 Generated with Claude Code