docs: Text Gate run-from-here + sticky edit design

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/plans/2026-06-26-textgate-run-from-here-design.md

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+# Text Gate — "Run from here" + sticky edit (design)
+
+**Goal:** Bring the Text Gate to parity with the Image Gate's "Run from here"
+affordance, plus a text-specific touch: keep the user's edited text across
+re-runs ("start from there").
+
+**Scope:** Frontend only — `web/text_gate.js`. No changes to `gates/textgate.py`,
+`gates/gate_bus.py`, or `gates/gate_server.py`. The gate already re-arms and
+re-pauses on every run (`GateBus.arm` → `wait_payload`) and `IS_CHANGED` returns
+`NaN`, so re-queuing the prompt is enough to "resume": cached upstream means the
+gate re-pauses near-instantly.
+
+## State machine
+
+The node currently has no explicit state. Add three:
+
+- **idle** — before the first run. Pass shown, Run-from-here hidden.
+- **paused** — socket `datasete-textgate-show` arrived. Textarea editable &
+  populated, **▶ Pass** shown, **Run from here** hidden, status `edit, then Pass`.
+- **passed** — after Pass click. Textarea keeps the edited text, **Pass** hidden,
+  **▶ Run from here** shown, status `passed — Run from here to re-run`.
+
+**Run from here** click → `app.queuePrompt(0, 1)` with `app.queuePrompt(0)`
+fallback — copied verbatim from the Image Gate's `queueFromHere`.
+
+## Sticky edited text
+
+The Image Gate keeps its mask sticky; the Text Gate keeps its text. The live
+textarea IS the sticky store, gated by the last-seen input:
+
+- Track `node._tgInput` = the last incoming text the server pushed.
+- On each re-pause with `incoming`:
+  - if `incoming === node._tgInput` (upstream unchanged — the Run-from-here
+    case) → **keep** the current textarea value, so the gate re-runs *your*
+    edited version (including any edits made after Pass).
+  - else (a genuine upstream recompute) → overwrite the textarea with `incoming`.
+  - always set `node._tgInput = incoming`.
+
+Net: "Run from here" re-runs your version, but a real upstream change still
+surfaces instead of hiding behind a stale edit. `_tgInput` is per-session
+(not serialized) — a page reload starts fresh, which is fine.
+
+## Verification
+
+- `node --check web/text_gate.js` (no JS test harness in the repo — consistent
+  with the other `web/*.js`).
+- Manual: pause → edit → Pass → button appears → Run-from-here re-pauses showing
+  your edited text → downstream re-runs; change something upstream → new input
+  shows.
+
+## Dropped (YAGNI)
+
+- A separate "↺ reset to input" button — the upstream-change detection covers the
+  stale-edit footgun.
+- Any backend auto-pass / bypass mode — not requested.