fix(prd): keep a PRD it cannot read so its number is not reissued

listPrds discarded any PRD whose readFileSync threw. That contradicts the
rest of the same loop: a PRD whose front matter will not parse is kept on
the slug and "?" fallbacks, which two existing tests assert.

The consequence is not a missing row. nextId takes its max from this list,
so dropping a PRD hands its number straight back out and two PRDs end up
numbered the same, in a scheme where the number is the identity. A
committed symlink whose target is not checked out is enough to trigger it:
readFileSync throws ENOENT, so it arrives from a plain clone.

Keep the entry on the same fallbacks the unparseable case already uses.
The id stays reserved and the index row keeps its link.

Author: clawedassistant

src/prd.mjs

@@ -229,7 +229,16 @@ export function listPrds(root = process.cwd()) {
         const t = l.match(/^title:\s*(.+)$/); if (t) title = unquoteYaml(t[1]);
         const s = l.match(/^status:\s*(.+)$/); if (s) status = unquoteYaml(s[1]);
       }
-    } catch { continue; }
+    // A file this cannot read is still a PRD, and its number is still taken.
+    // Dropping it contradicts what the rest of this loop does: a PRD whose
+    // front matter will not parse is deliberately kept on the slug/"?"
+    // fallbacks above rather than discarded. Worse, `nextId` takes its max
+    // from this list, so dropping one hands its number straight back out and
+    // two PRDs end up numbered the same — in a scheme where the number is the
+    // identity. A committed symlink whose target is not checked out is enough
+    // to trigger it: `readFileSync` throws ENOENT. Keep the entry on the same
+    // fallbacks; the id stays reserved and the index row keeps its link.
+    } catch { /* unreadable: keep it with the file-name fallbacks */ }
     out.push({ id: m[1], slug: m[2], title, status, file: name, path: file });
   }
   return out.sort((a, b) => a.id.localeCompare(b.id));

test/prd.test.mjs

@@ -317,3 +317,92 @@ test("regenerateIndex leaves an ordinary slugified PRD link untouched", () => {
     fs.rmSync(root, { recursive: true, force: true });
   }
 });
+
+// A PRD this cannot read is still a PRD, and its number is still taken. The
+// loop already keeps a PRD whose front matter will not parse, on the slug and
+// "?" fallbacks; a file that throws on read was the one case it discarded.
+// A committed symlink whose target is not checked out is enough to hit it —
+// git stores symlinks, so this arrives from a plain clone, not a corrupt disk.
+function dropDanglingPrd(root, name) {
+  fs.symlinkSync("./target-not-checked-out.md", path.join(root, "prd", name));
+}
+
+test("listPrds keeps a PRD it cannot read instead of dropping it", () => {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), "moshcode-prd-"));
+  try {
+    createPrd("improve search ranking", root);
+    dropDanglingPrd(root, "0002-search-ranking-v2.md");
+
+    const ids = listPrds(root).map((p) => p.id);
+    assert.deepEqual(ids, ["0001", "0002"], "the unreadable PRD must still be listed");
+    const prd = listPrds(root).find((p) => p.id === "0002");
+    // Same fallbacks the no-front-matter case already uses.
+    assert.equal(prd.title, "search-ranking-v2");
+    assert.equal(prd.status, "?");
+  } finally {
+    fs.rmSync(root, { recursive: true, force: true });
+  }
+});
+
+test("createPrd does not reissue a number an unreadable PRD already holds", () => {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), "moshcode-prd-"));
+  try {
+    createPrd("improve search ranking", root);
+    dropDanglingPrd(root, "0002-search-ranking-v2.md");
+
+    createPrd("add a dark mode toggle", root);
+
+    const numbered = fs.readdirSync(path.join(root, "prd"))
+      .filter((n) => /^\d{4}-/.test(n) && !n.startsWith("0000"))
+      .map((n) => n.slice(0, 4))
+      .sort();
+    assert.deepEqual(
+      numbered,
+      ["0001", "0002", "0003"],
+      `two PRDs must never share a number: ${numbered.join(", ")}`,
+    );
+  } finally {
+    fs.rmSync(root, { recursive: true, force: true });
+  }
+});
+
+test("regenerateIndex keeps a row for a PRD it cannot read", () => {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), "moshcode-prd-"));
+  try {
+    createPrd("improve search ranking", root);
+    dropDanglingPrd(root, "0002-search-ranking-v2.md");
+    regenerateIndex(root);
+
+    assert.equal(
+      indexRow(root, "0002"),
+      "| [0002](0002-search-ranking-v2.md) | search-ranking-v2 | ? |",
+    );
+  } finally {
+    fs.rmSync(root, { recursive: true, force: true });
+  }
+});
+
+// Control: a tree where every PRD reads cleanly must come out byte-identical,
+// so the fix cannot be read as churning existing indexes or listings.
+test("listPrds is unchanged when every PRD is readable", () => {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), "moshcode-prd-"));
+  try {
+    createPrd("improve search ranking", root);
+    dropPrd(root, "0002-import-notes.md", "Import notes");
+    regenerateIndex(root);
+
+    assert.deepEqual(
+      listPrds(root).map((p) => `${p.id}|${p.title}|${p.status}|${p.file}`),
+      [
+        "0001|Improve search ranking|Draft|0001-improve-search-ranking.md",
+        "0002|Import notes|Review|0002-import-notes.md",
+      ],
+    );
+    assert.equal(
+      indexRow(root, "Import notes"),
+      "| [0002](0002-import-notes.md) | Import notes | Review |",
+    );
+  } finally {
+    fs.rmSync(root, { recursive: true, force: true });
+  }
+});