feat(site/src/pages/AgentsPage): keep agent attachments in working blocks and list them under Attachments - #30788

• 11 rounds of coder-frontend-review (8 global roles), frontend-deep-review (8 project roles), and frontend-review (FE1 to FE10), read-only. Round 9 ran all 17 roles on b53897c; rounds 10 and 11 re-checked the comment-only fixes on 3e47d30 and 30007ac.
• Final verdicts: every checkpoint PASS except FE5 and FE6 (justified below). RP6's PASS requires the ConversationTimeline.tsx split follow-up listed above.
• Test audit: PASS through b53897c. Every finding not listed below was fixed.
• Codex: four rounds on 30007ac. Each of its five P2 findings was declined in its thread with evidence: a spinner for the one-commit hydration gap, the file name on the shared expired tile, the copy action for a text-and-file message that chatd never stores, gating the load button on hydration, and the ChatAttachments doc. Round 4 found no major issues.

Justified FAILs:

• FE5, no error text for a failed page: the transcript's pager shows the same retry-only state for the same query; follow-up.
• FE6 and SA6, the button disables while fetching and loses focus: the repo's load-more pattern (InboxPopover, HistorySidebar); follow-up for all three.

Dropped findings (finding: reason):

• RO6 stack split: the component is 94 lines, and the hiding needs the panel, so the halves are not independent.
• RP6 and RO5, split ConversationTimeline.tsx now: the PR adds call sites, a prop, and two flags; follow-up, and fix(site): split Working blocks at assistant text and scroll to their end on expand #30656 edits it.
• RO1 SidebarSectionHeader: a sidebar h2 with no aria-controls; the section uses the Radix Collapsible in SectionHeader.
• RO1 isFileRenderBlock: inline block.type checks are the grouping module's idiom.
• RO2 shared retry button: the two share only variant, size, and label.
• RO3 every helper: a one-line idiom with different predicates in two modules.
• RO3 shared guard with getMemberRow: two conditions, and fix(site): split Working blocks at assistant text and scroll to their end on expand #30656 rewrites getMemberRow.
• RO3 Omit over Pick: the Pick reuses the exported EarlierMessagesProps types.
• RO3 page-level spread: AgentChatPageView passes every prop explicitly.
• RO4 move isAgentAttachmentOnlyRow: it takes the grouping module's row type and sits beside getRowBlocks.
• RO5 transcript focus ring: intended; it matches the text-preview button.
• SD1 inline single-use story constants, and repeated fixture values: FE9 asks for named spread constants.
• SD2 { message } wrapper: retyping moves the map into ConversationTimeline.tsx, which fix(site): split Working blocks at assistant text and scroll to their end on expand #30656 edits.
• SA2 cva for fullWidth: one boolean in a pre-existing component.
• TN4 inline type imports: the repo's style for mixed imports.
• TN4 ChatStoreHandle: ChatStore is the exported type; the handle is a file-local alias.
• TN4 named FileCardProps: the file types its components inline.
• TN4 GetRowBlocksOptions: named like GroupWorkingBlocksOptions.
• TN5 AgentAttachment beside readAgentAttachmentText: that one reads user uploads, in another module.
• TN6 copy: the repo's paged empty state (SessionTimeline.tsx) and the transcript's retry label.
• CD1 getAgentAttachments doc: it states the ordering and the upload exclusion.
• CD1 trim exported docs: AGENTS.md requires docs on exported symbols.
• CD4 isHydratingMessages comment: pre-existing and consistent with its source.
• CD5 consumers in the EarlierMessagesProps doc: the doc states the contract.
• splitRowBlocks doc: the base text stays; a comment at the file condition gives the reason.
• Hydration comment placement: it sits on the operand it explains.
• Deleted NotVisible comment: this PR made it false.
• TS1 and TS5 NotVisible assertions: pre-existing.
• TS7 panel story with hasMoreMessages: tsc enforces the forward; WithEarlierMessages is the visual.
• TS7 streamed-file story: live rows share the getRowBlocks call.
• TS7 text-plus-file case and ChatError story: the grouping test fails on the same break; no new state.
• TS7 raster image fixture: grouping treats every file part alike.
• TS7 text and a file in one message: chatd persists a file as its own message; the unit test covers the branch.
• Play-function assertions and a collapse test: plays drive state, and Radix owns collapsing.
• useChatMessages unit test: a moved derivation with no new logic.
• Drop LoadingMessages and LiveMessageArriving: each catches a call-site break (test audit).
• A store per story, built in render: as ChatPageContent.stories does.
• NotVisible capture shows the section: it renders whatever isVisible is.
• RP4 hoist the .map callback: a single-use wrapper (site/AGENTS.md).
• RP5 useChatMessages as a function: it owns two subscriptions that three components share.
• RP8 pre-existing render helpers: unchanged; the split follow-up covers them.
• Per-render derivations and a second subscription: pure derivations; only the queries are gated.
• useFileProbes() before the branches: hooks cannot be conditional, and the default context is safe.
• DF5 share probes with the panel: FileCard never probes; both read chat.files, polled every 5 s while the chat runs.
• DF5 every loaded file evicted: a pre-existing deriveEvictedFileIds gap; follow-up.
• DF5 empty before query data: the page shows its loading view then.
• Spinner before the store fills: a one-commit window, so it would flash.
• Previous chat after a switch: the page remounts per chat with its own store.
• void onFetchMoreMessages(): fetchNextPage reports errors in its result, and the transcript calls it the same way.
• Later parts first within a message: later parts are newer.
• Up chevron when open: as ChatSectionHeader does.
• messageHelpers.ts imports chatAttachments.ts: the page already loads it; dpdm finds no cycle.
• Live status on a live row whose file is hidden: intended.
• m-0 on the empty state: index.css sets paragraph margins.
• FileCard's name omits "Download file", and the expired tile names no file: pre-existing; naming the file is a follow-up.

UAT observations, not failures:

• A file in a message that also holds text after the tool call is listed only under Attachments, as for any row outside a block. Round 3 first reported it as a FAIL; only DB-seeded rows had that shape, and 18 real-model runs never did.
• An evicted newest file keeps its link until a newer linked file exists (follow-up above).
• The panel scroller clips the bottom of a card's focus ring at its bottom edge.
• The load button has no aria-busy, and after a failure two buttons read "Retry loading earlier messages".
• One parallel step with two files renders both tool rows before both cards.
• The transcript's expired tile is 112px wide beside 384px cards, and its tooltip is mouse-only (pre-existing).