feat(assets): register output files as assets after prompt execution

Add ingest_existing_file() to services/ingest.py as a public one-call
wrapper for registering on-disk files (stat, BLAKE3 hash, MIME detection,
path-based tag derivation).

After each prompt execution in the main loop, iterate
history_result['outputs'] and register files with type 'output' as
assets. Runs while the asset seeder is paused, gated behind
asset_seeder.is_disabled(). Stores prompt_id in user_metadata for
provenance tracking.

Amp-Thread-ID: https://ampcode.com/threads/T-019cc013-1444-73c8-81d6-07cae6e5e38d
Co-authored-by: Amp <amp@ampcode.com>

app/assets/services/__init__.py

@@ -23,6 +23,7 @@ from app.assets.services.ingest import (
     DependencyMissingError,
     HashMismatchError,
     create_from_hash,
+    ingest_existing_file,
     upload_from_temp_path,
 )
 from app.assets.database.queries import (
@@ -72,6 +73,7 @@ __all__ = [
     "delete_asset_reference",
     "get_asset_by_hash",
     "get_asset_detail",
+    "ingest_existing_file",
     "get_mtime_ns",
     "get_size_and_mtime_ns",
     "list_assets_page",

app/assets/services/ingest.py

@@ -26,6 +26,7 @@ from app.assets.helpers import normalize_tags
 from app.assets.services.file_utils import get_size_and_mtime_ns
 from app.assets.services.path_utils import (
     compute_relative_filename,
+    get_name_and_tags_from_asset_path,
     resolve_destination_from_tags,
     validate_path_within_base,
 )
@@ -128,6 +129,42 @@ def _ingest_file_from_path(
     )
 
 
+def ingest_existing_file(
+    abs_path: str,
+    user_metadata: UserMetadata = None,
+    extra_tags: Sequence[str] = (),
+    tag_origin: str = "automatic",
+    owner_id: str = "",
+) -> IngestResult:
+    """Register an existing on-disk file as an asset.
+
+    Handles stat, BLAKE3 hash, MIME detection, and path-based tag derivation.
+    Deduplicates by hash (same content → same Asset, new AssetReference).
+    """
+    size_bytes, mtime_ns = get_size_and_mtime_ns(abs_path)
+
+    digest, _ = hashing.compute_blake3_hash(abs_path)
+    asset_hash = "blake3:" + digest
+
+    mime_type = mimetypes.guess_type(abs_path, strict=False)[0]
+
+    name, path_tags = get_name_and_tags_from_asset_path(abs_path)
+    tags = list(dict.fromkeys(path_tags + list(extra_tags)))
+
+    return _ingest_file_from_path(
+        abs_path=abs_path,
+        asset_hash=asset_hash,
+        size_bytes=size_bytes,
+        mtime_ns=mtime_ns,
+        mime_type=mime_type,
+        info_name=name,
+        user_metadata=user_metadata,
+        tags=tags,
+        tag_origin=tag_origin,
+        owner_id=owner_id,
+    )
+
+
 def _register_existing_asset(
     asset_hash: str,
     name: str,