image input pipeline: content-hash cache, data-url vision, picture_edit real

specs/SPEC-004-images.md

@@ -37,3 +37,53 @@ The translate-before-draw step is deleted: the model's picture prompt
 reaches the image API verbatim (current image models handle
 Norwegian/German natively). The `translate()` method and its
 `fix-model` dependency are gone (closes D-009).
+
+## Input pipeline (FDB-010)
+
+Attachments live in a content-hash cache
+(`<history-directory>/images/<sha256>.<ext>`, index in the store,
+schema v4). Active only with a store; without one the legacy CDN-URL
+path remains.
+
+### IMG-10 — Attachments are ingested at message time (coverage: test)
+
+Every image attachment is downloaded immediately (timeout, size cap
+`image-max-bytes` default 8 MB) and stored under its content hash.
+Only sniffed png/jpeg/gif/webp bytes are accepted — extension and
+declared MIME are ignored (attacker-controlled). Rejected content is
+dropped and logged (D11 root fix + cache-abuse hardening).
+
+### IMG-11 — Vision reads from the cache, never CDN URLs (coverage: test)
+
+Vision parts are `data:` URLs built from cached bytes. Discord's
+signed, expiring CDN URLs never reach the model or the history.
+
+### IMG-12 — The cache is capped and aged (coverage: test)
+
+`image-cache-mb` (default 500) LRU-evicts oldest-first;
+`image-cache-ttl-days` (default 90) ages entries out. Eviction always
+removes file and index row together.
+
+### IMG-13 — picture_edit edits the newest channel images (coverage: test)
+
+`picture_edit=true` calls `images.edit` with up to the 4 newest
+cached images of the answer channel as inputs (API max is 16; 4 keeps
+prompts sane). An empty cache falls back to plain generation — the
+flag alone must never fail a reply.
+
+### IMG-14 — Deletion propagates to the cache (coverage: test)
+
+Deleting a Discord message purges its cached images; `!forgetme`
+purges all of the user's images — files and rows (extends
+SAF-08/MEM-09).
+
+### IMG-15 — Generated images join the cache (coverage: test)
+
+Bot-generated images are ingested like uploads (user `assistant`), so
+"make a variant of that" remix chains work on the bot's own output.
+
+### IMG-16 — The prompt announces editable images (coverage: test)
+
+When the answer channel has cached images, the context suffix states
+how many and that `picture_edit=true` edits the newest — the model
+cannot use a capability it does not know about.