scripts/encoding.py: Stage 1 dual-implementation consolidation (Track 1 Finding 11)

Consolidates four extract paths and two extract-chunk-embed-write pipelines
into a single shared encoding module. Fixes the embedder lifecycle
divergence between watcher and /api/reindex (no more 200MB reload per
reindex click) and unifies failure tracking so /api/reindex failures now
surface in SettingsPanel "Ingest Health".

New files:
- scripts/encoding.py — extract_text, chunk_text, chunk_and_embed,
  write_embeddings_batch
- scripts/failures.py — record_ingest_failure, resolve_ingest_failure
  (shared by watcher.py and ingest.py)

Refactored:
- scripts/watcher.py — drops local extract/chunk/embed implementations
  and CHUNK_SIZE/CHUNK_OVERLAP/SUPPORTED constants; imports from encoding
  and failures. Now writes ingest_failures row on empty-text-extract
  (was silent return 0).
- scripts/ingest.py — substantial rewrite. Exposes ingest_directory(folder,
  embedder=None) for in-process invocation; CLI back-compat preserved via
  ingest_folder wrapper. Module-level SentenceTransformer load removed.
- scripts/corpus_integrity.py — imports extract_text from encoding;
  extract_text_for_retry function removed.
- scripts/api.py — /api/reindex rewritten with BackgroundTasks (uses
  module-level embedder; no subprocess); new /api/reindex/status endpoint
  reading ~/aaronai/reindex_status.json; /api/corpus/retry imports
  extract_text from encoding; INGEST_SCRIPT constant removed (dead after
  this refactor); 409 reentrance guard prevents double-click stomping.

Behavior changes:
- /api/reindex no longer subprocess.Popens; runs in FastAPI BackgroundTasks
  threadpool, doesn't block API thread.
- /api/reindex no longer reloads SentenceTransformer on each click.
- /api/reindex failures newly write to ingest_failures (visible in
  SettingsPanel "Ingest Health" — badge will jump on first reindex).
- New embeddings rows always have created_at = NOW() (canonical, server-side).
- New embeddings rows always include metadata.folder field (None when not
  derivable).
- /api/reindex returns 409 on second click while a job is running.
- New /api/reindex/status endpoint for polling.

Existing 9,815 NULL created_at rows remain unchanged; backfill is a
separate decision if desired.

199 insertions, 256 deletions across 6 files (codebase shrinks net).

Found by Track 1 inventory 2026-05-02 (Finding 11 / cross-cutting F11).
Pre-commit verification: BackgroundTasks already imported, sys.path
resolves correctly via script-path semantics, static import clean.

scripts/corpus_integrity.py

@@ -23,6 +23,9 @@ from datetime import datetime
 import psycopg2
 from dotenv import load_dotenv
 
+sys.path.insert(0, str(Path(__file__).parent))
+from encoding import extract_text
+
 load_dotenv(Path.home() / "aaronai" / ".env", override=True)
 
 NEXTCLOUD_PATH  = "/home/aaron/nextcloud/data/data/aaron/files"
@@ -103,28 +106,6 @@ def get_ingest_failures():
     return failures
 
 
-def extract_text_for_retry(filepath):
-    path = Path(filepath)
-    suffix = path.suffix.lower()
-    try:
-        if suffix == ".docx":
-            from docx import Document as D
-            return "\n".join(p.text for p in D(path).paragraphs if p.text.strip())
-        elif suffix == ".pdf":
-            from pypdf import PdfReader
-            return "".join(p.extract_text() + "\n" for p in PdfReader(path).pages if p.extract_text())
-        elif suffix == ".pptx":
-            from pptx import Presentation
-            prs = Presentation(path)
-            return "\n".join(shape.text for slide in prs.slides for shape in slide.shapes
-                             if hasattr(shape, "text") and shape.text.strip())
-        elif suffix in {".txt", ".md"}:
-            return path.read_text(encoding="utf-8", errors="ignore")
-    except Exception as e:
-        print(f"WARNING: extraction failed {path.name}: {e}", file=sys.stderr)
-    return ""
-
-
 def queue_for_retry(source, full_text, filepath):
     try:
         pg = get_pg()
@@ -188,7 +169,7 @@ def run_reconciliation(fix=False):
     if fix and neither:
         print(f"Auto-queuing {len(neither)} gap files...")
         for finfo in neither:
-            text = extract_text_for_retry(finfo["filepath"])
+            text = extract_text(Path(finfo["filepath"]))
             if text.strip():
                 if queue_for_retry(finfo["source"], text, finfo["filepath"]):
                     auto_queued.append(finfo["source"])