docs(tui): describe shell tails as frame-coalesced repaints

The host subscribes to feed appends and repaints on the next
animation frame. Clocks run on a Timeline only while sticky chrome
or a live lane needs them. Idle does not arm an interval.

Author: TheGreatAxios

docs/TUI-inline-eval.md

@@ -29,21 +29,21 @@ Nothing in the 0.6.4 types is an inline-mode renderable, an alternate inline sce
 - overlay selectors (empty-state fail-close, painted-id accept, shared list viewport)
 - the prompt kill ring
 
-A raw scrollback log also has no place for the shell-output preview the host paints on a timer. Sticky polling exists because the preview is a zone in the fullscreen tree, not a line already committed to scrollback.
+A raw scrollback log also has no place for the shell-output preview the host repaints from feed appends, coalesced on one animation frame, or for sticky chrome clocks that run on a renderer Timeline only while needed. That paint exists because the preview is a zone in the fullscreen tree, not a line already committed to scrollback.
 
 ## What stays
 
 - `src/tui/shell/layout.ts` applies terminal geometry: floors, prompt-row sync, landing split, relayout inputs.
 - `src/tui/geometry/zones.ts` defines the floors and the collapse order the layout refuses to violate.
 - `src/tui/shell/chrome.ts` `relayout` is the live entry that re-resolves the tree when visibility, prompt rows, or overlay mode change.
-- The `stickyPoll` interval in `src/tui/product-host.ts` keeps the shell-output preview and sticky chrome clocks painted. It is not scrollback.
+- Feed subscriptions and a renderer Timeline in `src/tui/product-host.ts` keep the shell-output preview and sticky chrome clocks painted. Idle does not arm an interval. Neither is scrollback.
 
 ## Deleted if inline mode were adopted
 
 It is not adopted. If it were, the deletion this record refuses is:
 
 - `shell/layout.ts`, the `geometry/zones.ts` floors, and `chrome.ts` relayout would be deleted or bypassed for a scrollback-only writer.
-- `stickyPoll` would go, because a raw scrollback commit has no sticky zone to repaint.
+- The host's shell-output subscription and Timeline would go, because a raw scrollback commit has no sticky zone to repaint.
 
 Those files stay. Bypassing them for `writeToScrollback` would drop the floors, the single scroll lease, overlay selectors, and the prompt kill ring. None of that is implied by a scrollback snapshot.
 

docs/TUI.md

@@ -116,13 +116,13 @@ plus up to three dim tail lines of the command's live output and — when the
 feed window holds more than three lines — the same dim `⋯ +N lines` elision
 marker as the settle preview, `N` counting lines within the live window (the
 feed keeps only the most recent 8 KiB). The output
-travels through a polled bounded feed (`src/session/shell-output-feed.ts`),
+travels through a bounded feed (`src/session/shell-output-feed.ts`),
 not a reactor event: the plugin appends chunks (capped at an 8 KiB tail per
-call, emitting at most once per 100 ms plus a final flush at settle), and
-the product host's sticky poll reads the feed snapshot every 200 ms and
-repaints the pending row frame-coalesced. Nothing from the feed is
-persisted. When the feed is not wired (tests, the demo shell), the row
-renders exactly as before — silent degradation.
+call, emitting at most once per 100 ms plus a final flush at settle). The
+product host subscribes to those appends and repaints the pending row from
+the feed snapshot, coalesced onto one animation frame. Nothing from the
+feed is persisted. When the feed is not wired (tests, the demo shell), the
+row renders exactly as before — silent degradation.
 
 At settle the live tail is replaced by a preview of the full output: its
 last three lines plus a dim `⋯ +N lines` elision marker when more were
@@ -303,9 +303,9 @@ user follow-ups untouched.
 stack-only (`layoutMode: "stack"`, `railWidth: 0`); the zone max is
 `AGENTS_PANEL_MAX_VISIBLE + 1` (lanes plus a trailing `+N more`). Finished
 lanes (done / failed / cancelled / interrupted) linger for
-`AGENTS_PANEL_LINGER_MS` (4s) after `finishedAt`, then drop. Product-host sticky
-poll uses
-`agentsChromeNeedsSticky` so clocks and linger stay fresh; while sticky is
+`AGENTS_PANEL_LINGER_MS` (4s) after `finishedAt`, then drop. The product host
+arms a renderer Timeline only while sticky chrome or a live lane needs it
+(`agentsChromeNeedsSticky`); idle does not arm an interval. While sticky is
 needed it **does not** call `bridge.syncAgentProgress` — chrome owns the live
 clocks.
 
@@ -1058,10 +1058,10 @@ terminal. It cannot observe:
 
 - **Real paint.** Tests assert on the shell's in-memory row/rect state, not
   on what a terminal emulator actually draws to a screen buffer.
-- **The live shell tail's wall clock.** The feed itself is pure and the
-  cadence is injectable, so the live tail is headless-testable by driving a
-  fake feed and a fake clock through the same sync path the sticky poll
-  uses; what the harness cannot see is real-time emission timing.
+- **The live shell tail's wall clock.** The feed itself is pure, so the
+  live tail is headless-testable by appending to a fake feed and repainting
+  through the host subscription on the next frame; what the harness cannot
+  see is real-time emission timing.
 - **Modifier reporting.** Whether a real terminal can report Shift+Enter,
   Alt+letter, or similar modifier combinations depends on the terminal
   negotiating the kitty keyboard protocol (or an equivalent) with the actual