T7.7 - CR-007/D8: the sheet travels with the package, and opens offline

The field wants the specific PDF attached, not a link to a Bluebeam session.

Storage: a new wp_files table (Alembic f3a9d2c1e8b7, additive only) holding
the BYTES in the same database as everything else - the Aug 18 decision: a
backup that excludes the drawings is a backup you cannot restore from. The
D8 numbers bound the cost and are enforced ON THE SERVER as well as in the
browser: 5MB a file (413, naming the limit), PDF and image mimes only (400,
naming what is accepted), 2GB a project (413 naming the ceiling; response
flags the 80% warning). The ceiling is env-overridable for tests; the shipped
default is the decision, asserted from source.

The package record carries a server-owned meta mirror (data.files): the
upload/patch/delete routes rewrite it, and the upsert re-asserts the stored
copy over whatever a client sends - a save from a browser that had not seen
an upload land cannot erase the list.

Creator: uploads live beside the links (links still work), the limits and the
running project total sit ABOVE the picker (amber from 80%, red at full), a
refused file costs nothing but a toast and never leaves the browser (the
probe counts fetch calls), and each drawing has a description ("Tray section,
Level 3 east only") editable inline and persisted server-side. Uploads attach
to the saved record, so T4.3's autosave keeps the surrounding form safe (X8).

Export: uploads print with the package - name, size tag, description on the
attachments table, images inline as the sheet itself, PDFs as links.

Offline (D8): the service worker gains a drawings cache (cache-first on
/api/files/), and field.js prefetches ONLY the requesting user's assigned
packages - assignment-scoped by decision, not project-wide. The probe's first
offline check used CDP network emulation and PASSED FOR THE WRONG REASON: the
emulation binds to the page's session and the service worker fetches on its
own target, straight past it. The shipped check kills the server instead -
my drawing opens, the other package's does not, against a genuinely dead
network.

Field View: a Drawings section on the package detail, 44px rows, description
inline, inside the 390px screen.

Verification (each probe run alone): NEW tests/files_check.py 36/36; the
Alembic chain applied end-to-end to a scratch DB and the table verified.
Regressions: form_structure_check 50/51 (the standing F6 height gap),
frame_check 39/39.

Items: CR-007, D8 (X8 honored)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/reference/file-map.md

@@ -281,6 +281,7 @@ python tests/hold_check.py           # CR-015/A1/D4 - the hold clears, gates hol
 python tests/warning_check.py        # A2 - one warning, a badge from anywhere    17 checks
 python tests/triage_check.py         # A6 - the sidebar answers the stand-up      16 checks
 python tests/qa_gate_check.py        # CR-014/D2/D9/D10 - QA gate + capture sink  40 checks
+python tests/files_check.py          # CR-007/D8 - drawings upload + real offline 36 checks
 ```
 
 **Three probes were re-pointed at `T7.1`.** `sections_check.py` 5b drove the live