fix(inspect): video metadata carrier parity between Images and Inspect (#275)

* fix(video): select one prompt carrier from per-key or comment tags

Current ComfyUI savers write one container tag per key (prompt, workflow,
parameters, comfyassets_prompt_pairs); only the old VideoHelperSuite comment
envelope was read. select_video_carrier picks exactly one carrier in the
order per-key tags, comment envelope, description: the first with a role
key wins, else the first with a workflow, and carriers never merge.
Matroska upper-cased tag names fold on our side; differing fold-duplicates
fail the read like duplicate PNG keys, identical ones are one record.
Per-key values stay original-text; envelope objects are reserialized.

* fix(inspect): read per-key video prompt tags

The inspector asked ffprobe only for comment and description, so videos
written by core SaveVideo/SaveWEBM and current VideoHelperSuite (one tag per
key) were inspected as having no metadata. It now asks for
prompt,workflow,parameters,comfyassets_prompt_pairs,comment,description and
hands the tags to the shared carrier selector. ffprobe stdout is bounded at
the role and workflow budgets plus 64 KiB of envelope; past that it probes
once more without the workflow tag within the role budget and marks the
per-key workflow limited, while an over-budget envelope still fails the
read. Differing fold-duplicate tags fail like duplicate PNG keys.

* fix(video): scan videos written by current ComfyUI savers

The output scan and live monitor read container tags through
metadata_from_tags, which now delegates to the shared carrier selector, so
per-key prompt, workflow, parameters and comfyassets_prompt_pairs tags
(including Matroska upper-cased names) are ingested with the default
resolver profile exactly like the same graph in a PNG. Fold-duplicate tags
and null markers are skipped quietly. Pins the behavior with a mocked
ffprobe scan test and real MP4/MKV/WebM round trips when ffmpeg is present.

* docs(testing): document video carrier selection

Record the shared video carrier order (per-key tags, comment envelope,
description), the fold-duplicate rule, the 6 MiB + 64 KiB probe bound with
the role-only re-probe and limited workflow, and that scans read the same
carrier as the inspector.

* fix(inspect): size video probe bounds for JSON escaping, exact-case envelopes

ffprobe JSON-escapes tag text, so bounds measured on its stdout could mark a
video workflow limited, or fail a role record, that the identical PNG reads
within its decoded budget. The first probe now allows twice the role and
workflow budgets plus 64 KiB (12 MiB + 64 KiB) and the role-only re-probe
twice the role budget plus 64 KiB, leaving the decoded per-record budgets as
the only gate; a reader-level test reads near-budget quote-dense records as
PNG and as video and asserts identical metadata and formats.

Envelope keys (comment, description) are matched exactly as the legacy
readers did; only the four per-key carriers fold Matroska case. Fixtures can
write the legacy ilst comment atom (metadata_tags=False), and the docs now
say the admin scan reads the carrier while the live monitor still processes
images only, with a follow-up recorded in TESTING.md.

TESTING.md

@@ -332,7 +332,30 @@ becomes record format `limited` (no raw text, graph `limited`, roles and facts
 unaffected); other text chunks are skipped unread; byte-identical duplicates are
 accepted within a bounded read budget, while differing duplicates (and any duplicate
 role record over that budget) still fail. Other read bounds are unchanged: 8 MiB
-non-PNG header, 10,000 PNG chunks and a three-second ffprobe. Resolution under
+non-PNG header, 10,000 PNG chunks and a three-second ffprobe (per probe, at most two
+probes). Video containers are read through one shared carrier selector
+(`utils/video_metadata.select_video_carrier`, used by the inspector and by the admin
+scan): carriers are, in order, the per-key tags that current savers write (`prompt`,
+`workflow`, `parameters`, `comfyassets_prompt_pairs`, each `original-text`; Matroska
+upper-cased names fold on our side), then the old VideoHelperSuite `comment` JSON
+envelope, then `description` (object values are `reserialized-json`; envelope keys are
+matched exactly, as the legacy readers did, never folded). The first carrier holding a
+role key wins, otherwise the first holding a workflow, and carriers never merge. Two
+per-key tags folding to one key are a duplicate record: byte-identical ones are one
+record, differing ones fail the read. ffprobe is asked for exactly those six tags.
+Its JSON output escapes tag text (at most doubling it), so the stdout bounds are sized
+so that only the decoded per-record budgets above can fail or limit a record, and a
+video reads exactly as the identical PNG: the first probe allows twice the role and
+workflow budgets plus 64 KiB of envelope (12 MiB + 64 KiB); past that the inspector
+probes once more without the `workflow` tag within twice the role budget plus 64 KiB
+(4 MiB + 64 KiB) and the per-key workflow becomes `limited`, while an envelope over
+that bound still fails the read because it cannot be split. The admin scan reads the
+same carrier with the default resolver profile, so a per-key video links like the same
+graph in a PNG; the live monitor processes images only (unchanged, see the follow-up
+below) (`tests/test_utils_video_metadata.py`, `tests/test_api_admin.py`
+`TestScanReadsVideos`, `tests/test_api_prompt_inspector.py` `test_video_*`,
+`tests/test_inspection_response.py` `TestVideoProbeBoundsMatchPngBudgets`; the
+real-container round trips skip without ffmpeg). Resolution under
 `INSPECTION_PROFILE` bounds work, not graph size: 2,000 visits per candidate chain,
 20,000 in total, 64 link/JSON-container levels, 100,000 resolved characters, and a
 two 20,000-node ceilings: one over the top-level entries of the API prompt, and one
@@ -1656,6 +1679,12 @@ responsive production Viewer keeps its toolbar in the media panel and prompt det
 mobile toolbar collision. These are explicit remaining visual differences, not
 a whole-application or full-gallery/Viewer pixel-parity claim.
 
+Follow-up: monitor video support. The live image monitor (`utils/image_monitor.py`,
+`GalleryConfig.SUPPORTED_EXTENSIONS`) processes images only; videos written by
+ComfyUI savers reach the Library through the admin scan, which reads the shared video
+carrier. Accepting `VIDEO_EXTENSIONS` in the monitor and routing them through
+`read_video_metadata` is a separate, issue-linked change.
+
 Preserve raw logs, failed traces, paired PNGs, geometry, runtime versions and
 source hashes before later managed commands clear their output directories.
 Frontend baseline updates are additive through `coverage:update` only after