ios: add Agent attachments and shared transcript fade

ios/README.md

@@ -30,10 +30,69 @@ even if the HTTP acknowledgement is lost. Raw tool calls and results are hidden
 in the Agent transcript, including loaded history and live updates. History windows,
 date separators and scroll anchors use visible messages; raw merged history and
 cursors remain intact. Send failures, room errors and activity indicators remain
-visible. Attachments, model selection and tool cards belong to ordinary chats.
+visible. Model selection and tool cards continue to belong to ordinary chats.
 
 Agent contracts remain in `../docs/api/rest.md` and
-`../docs/api/streaming-chat.md`; this client requires no backend deployment.
+`../docs/api/streaming-chat.md`. ROOT attachments consume the coordinated v1
+contract (2026-10-14), now documented in the integrated API sources above.
+Attachment readiness requires the coordinated backend/runtime and existing public
+API bearer authentication. This iOS change does not deploy or configure them.
+
+### ROOT attachments
+
+The Agent composer exposes Files and Photo Library only when the authenticated
+descriptor advertises supported `capabilities.attachments.version == 1`. Missing,
+malformed, or unsupported capability keeps the client text-only. Ordinary chat
+attachments retain their existing inline format and behavior.
+Open-proxy HTTP 503 / WebSocket 4503 failures disable attachment selection while
+retaining draft descriptors and outbox retry identities; reconnect checks support.
+
+Files preserve their original bytes, including PDF, archives, text and HEIC files.
+Photo Library HEIC/HEIF selections are intentionally converted to bounded JPEG
+visual input with a matching `.jpg` filename. PNG/JPEG/GIF/WebP are validated as
+raster images; model input is static, with no claim of document or animation
+understanding. Safe original names supplied by the picker are retained; PhotosPicker
+may provide an export filename rather than the original Photo Library asset name.
+The production app does not request broad Photo Library access.
+
+Selection order is stable. One preparation/upload runs at a time, with per-item
+loading, upload, error, retry and removal. Sending requires every item to be ready;
+an empty caption can send ready attachments. Advertised limits are checked against
+v1 hard ceilings (8 files, 32 MiB total, 6 MiB/image, 8 MiB/file, 50 million pixels,
+16,384 pixels/axis). Quota snapshots are decoded but do not reserve space. Server
+messages/codes, quota details and Retry-After survive failures, including 409, 413,
+429 and 507. Removal cancels local work and removes the reference; it does not
+delete an uploaded server original.
+
+The caption, ordered upload UUIDs and ready descriptors are saved in a small atomic
+manifest under Application Support, scoped to the API base URL. Prepared bytes are
+staged in app-owned files (at most 8 MiB each and 32 MiB per draft); no inline bytes
+or tokens enter the outbox. Relaunch restores ready drafts and offers explicit retry
+for interrupted staged uploads with the same upload UUID. A selection interrupted
+before staging must be removed and selected again. Uploads suspend when the room
+stops; failed work does not automatically retry. Uploaded originals have no client
+expiration. After submission, the outbox owns the caption, ordered descriptors and
+stable request ID. A persisted draft identity recovers a crash during this handoff
+without creating a second send. Storage failure blocks submission rather than
+discarding a draft. Attachment receipts must acknowledge exactly the submitted IDs
+in order; matching canonical echoes still win ambiguous HTTP failures.
+
+History and queued/live messages decode only `metadata.agentAttachments` for ROOT.
+Cards retain filename, MIME, size and the optional server-provided `workspacePath`,
+which can be copied. The client never constructs a runtime path or sends one as a
+reference; leading-dot display filenames remain unchanged. Captions remain public
+text, including the server's fallback for attachment-only messages.
+
+Original downloads use the configured authenticated URLSession and API base
+(including `/api`), reject redirects, and verify exact size and SHA-256. At most two
+downloads run concurrently, with a 16 MiB in-memory cache discarded on configuration
+change. Queued/active cancellation and generation checks prevent stale previews
+from crossing configurations. Raster previews use bounded thumbnails; text previews
+are plain text, including HTML/SVG. Save/share exports exact original bytes to a
+temporary file removed when its card disappears or configuration changes. An app
+crash may leave a temporary export for normal OS temporary-directory cleanup.
+Image preview frames have fixed height to preserve scroll anchors during loading.
+Attachment modals track their own visibility without changing Quick Question state.
 
 ### Agent regression and Simulator checks
 
@@ -47,7 +106,10 @@ just screenshot build/agent-evidence/simulator.png
 ```
 
 `just test` runs reducer, cursor, outbox, presentation, shared-read and lifecycle
-regressions along with the existing app tests through Xcode on iPhone 16e.
+regressions along with attachment capability/metadata, multipart/auth/bytes/errors,
+HEIC conversion versus original-file preservation, ordered receipts, draft/outbox
+relaunch, cancellation, two-transfer concurrency and configuration isolation tests
+through Xcode on iPhone 16e.
 For interactive UI coverage, start the local fixture (Python with `aiohttp`):
 
 ```sh
@@ -71,6 +133,15 @@ admission/retry, tools, asynchronous replies, inactive sidebar unread counts,
 shared reads, reconnect/malformed replay, foreground recovery, long-history scroll
 anchors and multiline keyboard layout. The launch arguments select the fixture
 through ordinary API settings; no fixture mode is compiled into the application.
+Attachment cases exercise authenticated originals, safe text/raster display,
+history reload, capability absence and picker cancellation. The real Photo Library
+selection-to-send test is explicitly skipped: this iOS 26.5 XCTest environment has
+unreliable Photos authorization, callback isolation and synthetic-asset cleanup.
+Selection-to-send remains a manual/device pre-release check, not a validated UI
+path. The gate prevents photo mutations during the general UI suite. Synthetic
+HEIC conversion and original HEIC file preservation are covered by package tests.
+The fixture accepts multipart uploads, stable upload/message retries, structured
+errors and attachment receipts; it is not a runtime image-decoder or quota test.
 Use a fresh result-bundle path for each run. Check the same UI on iPad and with
 Simulator Reduce Motion enabled before release.