feat(library): add tags to many selected prompts and select every loaded prompt (#442)

The Library selection bar (D148) gets Add tags and select-all of the loaded
shelf, the legacy admin page's bulk Add Tags and select-all checkbox.

Add tags posts {prompt_ids, tags, expected_epoch} to
POST /prompt_manager/bulk/tags: in one BEGIN IMMEDIATE transaction the server
checks the storage epoch, normalizes the names as image tags are, gives each
Library parent only the names it lacks (casefold), finds or inserts tag rows
by exact name only when some prompt gets them, and skips prompts that would
pass 20 tags. Prompt tags only. Both bulk/tags forms refuse a non-object body
with 400.

Ctrl/Cmd+A in the grid and "Select all N loaded" in the bar select every
loaded prompt; the offer follows each loaded batch.

Closes #442

database/library_commands.py

@@ -23,6 +23,8 @@ _TOKEN = re.compile(r"[0-9a-f]{64}")
 _PROMPT_COLUMNS = ("category", "rating", "notes")
 # Ids per IN (...) read: well under SQLite's oldest bound-parameter limit (999).
 _BULK_CHUNK = 500
+# The tags one prompt may carry: what the editor's save accepts (``validate_tags``).
+MAX_LIBRARY_TAGS = 20
 
 
 class LibraryCommandError(Exception):
@@ -363,3 +365,88 @@ class LibraryCommandOperations:
                 "unchanged": len(current) - len(changed),
                 "not_found": len(prompt_ids) - len(current),
             }
+
+    def bulk_add_library_tags(
+        self, prompt_ids: list[int], tags: list[str], *, expected_epoch: str
+    ) -> dict:
+        """Add tags to many Library parents, all or nothing (#442).
+
+        Names are normalized once (trim, the vocabulary name rules, casefold
+        repeats folded, at most 20). A parent is given only the names it lacks,
+        compared with ``casefold`` against its own tags; registry rows are
+        found and inserted by their exact name, and only for names some parent
+        gets. A parent whose tags would pass 20 is skipped (``over_limit``) so
+        the editor can still save it. Pair and image tags are not touched.
+        """
+        from .annotations import ImageTagLimitError, normalize_image_tags
+
+        _validate_epoch(expected_epoch)
+        _validate_bulk_ids(prompt_ids)
+        prompt_ids = list(dict.fromkeys(prompt_ids))
+        too_many = f"At most {MAX_LIBRARY_TAGS} tags can be added at once"
+        try:
+            tags = normalize_image_tags(tags)
+        except ImageTagLimitError:
+            # Its message names images; this is a prompt route.
+            raise ValueError(too_many) from None
+        if not tags:
+            raise ValueError("tags must name at least one tag")
+        if len(tags) > MAX_LIBRARY_TAGS:
+            raise ValueError(too_many)
+        with self._pair_transaction() as conn:
+            epoch = self._library_epoch(conn, expected_epoch)
+            held = self._library_parent_tags(conn, prompt_ids)
+            additions, over_limit = {}, 0
+            for pid, names in held.items():
+                present = {name.casefold() for name in names}
+                missing = [name for name in tags if name.casefold() not in present]
+                if not missing:
+                    continue
+                if len(names) + len(missing) > MAX_LIBRARY_TAGS:
+                    over_limit += 1
+                    continue
+                additions[pid] = missing
+            wanted = list(
+                dict.fromkeys(n for names in additions.values() for n in names)
+            )
+            tag_ids = self._ensure_tags(conn, wanted)
+            now = utc_now_iso()
+            for pid, names in additions.items():
+                conn.executemany(
+                    "INSERT OR IGNORE INTO prompt_tags (prompt_id, tag_id) "
+                    "VALUES (?, ?)",
+                    [(pid, tag_ids[name]) for name in names],
+                )
+                self._ensure_library_parent(conn, pid)
+                conn.execute("UPDATE prompts SET updated_at=? WHERE id=?", (now, pid))
+            return {
+                "library_epoch": epoch,
+                "tags": tags,
+                "updated": len(additions),
+                "unchanged": len(held) - len(additions) - over_limit,
+                "not_found": len(prompt_ids) - len(held),
+                "over_limit": over_limit,
+            }
+
+    def _library_parent_tags(
+        self, conn: sqlite3.Connection, prompt_ids: list[int]
+    ) -> dict[int, list[str]]:
+        """The Library parents among ``prompt_ids`` and their own tag names."""
+        held: dict[int, list[str]] = {}
+        for start in range(0, len(prompt_ids), _BULK_CHUNK):
+            chunk = prompt_ids[start : start + _BULK_CHUNK]
+            marks = ",".join("?" for _ in chunk)
+            for (pid,) in conn.execute(
+                f"SELECT p.id FROM prompts p WHERE p.id IN ({marks}) "  # nosec B608
+                f"AND {_ELIGIBLE}",
+                chunk,
+            ):
+                held[pid] = []
+            for pid, name in conn.execute(
+                "SELECT pt.prompt_id,t.name FROM prompt_tags pt "  # nosec B608
+                f"JOIN tags t ON t.id=pt.tag_id WHERE pt.prompt_id IN ({marks})",
+                chunk,
+            ):
+                if pid in held:
+                    held[pid].append(name)
+        return held