Prepare v0.3.8 changelog and announcement

apps/marketing/src/content/changelog/v0.3.8.md

@@ -0,0 +1,52 @@
+---
+version: 0.3.8
+date: 2026-09-01
+title: Claude Fable 5.1, subagent messaging, and preview tools
+summary: This release adds Claude Fable 5.1, direct messaging to Codex subagents, background markers in the agent roster, and browser preview find and error reporting, plus several UI and streaming fixes.
+githubRelease: https://github.com/Threadlines/threadlines/releases/tag/v0.3.8
+highlights:
+  - title: Claude Fable 5.1 in the model picker
+    description: Claude Fable 5.1 joins the curated Claude catalog with its full reasoning options, including Ultracode, and its native 1M context. The bare fable alias now resolves to it, matching Claude Code 2.1.257, and Fable 5 stays available for older CLIs.
+    evidence:
+      - 5a750b1f
+  - title: Message Codex subagents directly from the Agents view
+    description: When a Codex subagent is live, open its drill-in to send a one-line reply. Enter sends the message and it appears in the subagent transcript like any other turn. The server routes these replies so steering a subagent no longer requires relaying through its parent.
+    evidence:
+      - e038ffab
+      - c9889a76
+  - title: See backgrounded agents and real task depth
+    description: Agents started in the background show a "background" note in the roster meta line while they are live. Task depth and ambient housekeeping are reported so background work no longer counts as active waiting in snapshots and summaries.
+    evidence:
+      - ffd44a47
+      - b5fc0def
+  - title: "Browser preview: find bar, page errors, and preview controls"
+    description: The preview browser includes an in-page find bar and explicit page error reporting. Desktop preview controls are wired through the app so you can use preview commands from the desktop UI, and picked-element context is preserved across drafts and messages.
+    evidence:
+      - eea05ed5
+alsoImproved:
+  - description: Non-blocking agent questions no longer pause the turn or show the interface as waiting unless explicitly marked blocking.
+    evidence:
+      - f59b9673
+  - description: Installed plugin and skill entries show provider icons in settings so installed extensions are easier to identify.
+    evidence:
+      - a87d8e3b
+  - description: Automatic approval results no longer render as warning rows when an auto review is approved, reducing false warning noise in the timeline.
+    evidence:
+      - f0730d2e
+  - description: Subagent streaming overhead was reduced so transcripts and the agent roster stay responsive during heavy multi-agent activity.
+    evidence:
+      - 1a07f4fe
+  - description: The Codex app-server client now speaks protocol 0.150.1, so the newest Codex CLI resumes threads, reports usage, and surfaces the new plan types without errors.
+    evidence:
+      - dac75992
+social: |-
+  Threadlines v0.3.8 is out 🧵
+
+  • Claude Fable 5.1 in the picker
+  • Message Codex subagents directly
+  • Background agents shown in roster
+  • Browser preview find and page errors
+  • Codex CLI 0.150 support
+
+  Release notes: https://github.com/Threadlines/threadlines/releases/tag/v0.3.8
+---