fix(#4678): resolve :LINE citations against their underlying files (#4719)

* fix(#4678): check :LINE citations instead of dropping or misreporting them

cmdVerifyReferences had two opposite failures on citations carrying a
trailing line suffix. The backtick extractor anchored the closing
backtick right after the extension, so `src/foo.ts:42` matched neither
regex and was silently dropped -- an all-line-numbered document
reported {valid:true, found:0, missing:[], total:0}, indistinguishable
from one with no citations. The @-extractor treated ':' as a legal path
character, so @src/foo.ts:42 was probed with the suffix glued on and a
resolvable file was reported missing.

Strip the :N / :N-M suffix (stripLineSuffix) before existsSync in both
loops -- for filesystem resolution only; found/missing keep reporting
the original citation text -- and let the backtick regex accept the
optional suffix so those citations are counted at all. URL skip,
template-placeholder skip, dedup, ~/ expansion and the output contract
are unchanged. Whether a line number past EOF counts as missing is an
open design question and stays out of scope.

* chore(#4678): backfill changeset pr field with PR number

The fragment shipped as the documented pr: 0 placeholder; the merge
gate requires pr > 0 before a fragment can land, so backfill 4719 now
that the PR number exists.

---------

Co-authored-by: TwistedRiCen <16397953+TwistedRiCen@users.noreply.github.com>
Co-authored-by: Tom Boucher <trekkie@nomorestars.com>

tests/verify.test.cjs

@@ -1397,6 +1397,58 @@ describe('verify references command', () => {
     assert.strictEqual(output.total, 0, `Expected total 0 (template skipped): ${JSON.stringify(output)}`);
   });
 
+  test('#4678: line-numbered citations are checked, not dropped or misreported', () => {
+    fs.writeFileSync(path.join(tmpDir, 'src', 'app.js'), 'console.log("app");\n');
+    fs.writeFileSync(path.join(tmpDir, 'src', 'utils', 'helper.js'), 'module.exports = {};\n');
+    const filePath = path.join(tmpDir, '.planning', 'phases', '01-test', 'doc.md');
+    fs.writeFileSync(filePath, [
+      '- `src/gone.ts:99`',
+      '- `src/utils/helper.js:7`',
+      '- @src/app.js:42',
+      '- @src/gone.ts:1',
+      '- `src/utils/helper.js`',
+      '- `src/gone.ts`',
+      '- @src/app.js',
+      '',
+    ].join('\n'));
+
+    const result = runGsdTools('verify references .planning/phases/01-test/doc.md', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+
+    const output = JSON.parse(result.output);
+    // Every citation must land in exactly one bucket: the three gone.ts citations
+    // (with and without the line suffix, in both citation styles) are missing;
+    // the rest resolve.
+    assert.strictEqual(output.total, 7, `Expected total 7: ${JSON.stringify(output)}`);
+    assert.strictEqual(output.found, 4, `Expected found 4: ${JSON.stringify(output)}`);
+    assert.ok(
+      output.missing.includes('src/gone.ts:99'),
+      `Expected missing to keep the original citation text "src/gone.ts:99": ${JSON.stringify(output.missing)}`
+    );
+    assert.ok(
+      output.missing.includes('src/gone.ts:1'),
+      `Expected missing to keep the original citation text "src/gone.ts:1": ${JSON.stringify(output.missing)}`
+    );
+    assert.ok(
+      output.missing.includes('src/gone.ts'),
+      `Expected missing to include "src/gone.ts": ${JSON.stringify(output.missing)}`
+    );
+    assert.strictEqual(output.valid, false, 'should be invalid');
+  });
+
+  test('#4678: an all-missing line-numbered document is not reported valid', () => {
+    const filePath = path.join(tmpDir, '.planning', 'phases', '01-test', 'doc.md');
+    fs.writeFileSync(filePath, ['- `src/gone.ts:99`', '- `src/also-gone.ts:1-20`', ''].join('\n'));
+
+    const result = runGsdTools('verify references .planning/phases/01-test/doc.md', tmpDir);
+    assert.ok(result.success, `Command failed: ${result.error}`);
+
+    const output = JSON.parse(result.output);
+    assert.strictEqual(output.total, 2, `Expected total 2: ${JSON.stringify(output)}`);
+    assert.strictEqual(output.missing.length, 2, `Expected both citations missing: ${JSON.stringify(output)}`);
+    assert.strictEqual(output.valid, false, `Must not report valid: ${JSON.stringify(output)}`);
+  });
+
   test('returns error for nonexistent file', () => {
     const result = runGsdTools('verify references .planning/phases/01-test/nonexistent.md', tmpDir);
     assert.ok(result.success, `Command failed: ${result.error}`);