docs(rfc): mark Transparent Stream RFC Accepted + add spike note (#3820) (#3864)

Direction confirmed by @nesquena (Discord) and the RFC is merged (#3862), so
flip Status Proposed -> Accepted. Also record the settled-path spike result on
integration point A: ~31 lines, no new data, compact previews via the existing
buildToolCard, and reload consistency for free from the rebuild cleanup; DOM
insertion order verified with a node harness. Doc-only.

Co-authored-by: Frank Song <franksong2702@gmail.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: nesquena-hermes <nesquena+hermes@gmail.com>

docs/rfcs/transparent-stream-activity-mode.md

@@ -1,8 +1,9 @@
 # Transparent Stream — A Chronological Activity Display Mode
 
-- **Status:** Proposed
+- **Status:** Accepted (direction confirmed by @nesquena; RFC merged via [#3862](https://github.com/nesquena/hermes-webui/pull/3862))
 - **Author:** @franksong2702
 - **Created:** 2026-06-09
+- **Updated:** 2026-06-09
 - **Tracking issue:** [#3820](https://github.com/nesquena/hermes-webui/issues/3820)
 - **Parent contract:** [Live-to-Final Assistant Replies](./live-to-final-assistant-replies.md) ([#3400](https://github.com/nesquena/hermes-webui/issues/3400) / #3401 / #3741)
 
@@ -167,6 +168,17 @@ drift; the function names are the durable anchors.
   identified, and the highest-value fix because it kills the settle/reload
   collapse.
 
+  **Spike-validated (2026-06-09).** A throwaway prototype against `master`
+  confirmed this branch is ~31 lines and needs no new data: `activityOrder` is
+  already sorted chronologically, and the standalone `buildToolCard(tc)` /
+  `_thinkingActivityNode(text)` builders supply the compact-preview cards
+  directly (so acceptance criterion 3 is met by existing code on this path).
+  Reload/re-render consistency (criterion 4, settled) comes for free because the
+  rebuild cleanup already removes `.tool-card-row` and `.agent-activity-thinking`
+  before each render. DOM insertion order — including the shared-anchor fallback
+  case where two activity entries resolve to the same assistant segment — was
+  verified with a small node harness. The spike was local-only and not pushed.
+
 - **B. Live** — `ensureLiveWorklogShell()` and the live
   `reasoning`/`tool`/`interim_assistant` handlers. The transparent branch must
   **not** just fall back to the old `thinkingRow` (that is the path that pushed