feat: better chat support for thinking

PLAN.md

@@ -13,11 +13,11 @@ sessions, tools, and turn orchestration.
 | Area | Status | Available now | Still open |
 | --- | --- | --- | --- |
 | App shell | Implemented | Native multi-window Iced app, Codex-inspired layout, native Application/Edit/Window menus, Preferences panel, Model Manager, and streaming composer | Native app release packaging |
-| Projects and sessions | Implemented for metadata | Native folder picker, project-name dialog, create/select/delete projects and sessions | Transcripts, KV payloads, rename/archive, and model binding |
-| Persistence | Implemented for metadata and preferences | SQLite in Application Support, Diesel ORM, embedded migrations, constrained defaults and CRUD tests | Messages, downloaded-artifact metadata, and session-runtime migrations |
+| Projects and sessions | Implemented with transcripts | Native folder picker, project-name dialog, create/select/delete projects and sessions, and durable structured chat history | KV payloads, rename/archive, and model binding |
+| Persistence | Implemented for metadata, preferences, and chat | SQLite in Application Support, Diesel ORM, embedded migrations, constrained defaults, streamed message updates, and reopen tests | Downloaded-artifact metadata and session-runtime migrations |
 | Model runtime | DeepSeek Flash vertical implemented | Rust-owned mmap/model/session graph, reused Metal kernels, 2K compressed-attention generation, DS4 sampling, lazy background loading, cancellation, and idle unloading | Ratio-4 sparse indexer beyond 2K, DSpark/SSD/steering, GLM/Pro, KV checkpoint persistence, and shared acquisition for HTTP |
 | Local endpoint | Not started | Nothing listening | OpenAI-compatible HTTP and streaming surfaces |
-| Agent | Basic local chat implemented | Multi-turn role rendering, streamed DeepSeek Flash text, composer send/stop, and in-memory transcript | Durable transcripts, reasoning presentation, tools, approvals, compaction, statistics, and KV-backed resume |
+| Agent | Basic local chat implemented | Multi-turn role rendering, structured reasoning disclosure, streamed DeepSeek Flash text, composer send/stop, and durable transcript rehydration | Tools, approvals, compaction, statistics, and KV-backed resume |
 | A2UI | Future extension | bDS2 provides the reference structured render-tool contract | Native inline surfaces for local chat after core chat and tools are stable |
 | Dev brain | Not started | No vault access | Obsidian vault selection, durable access, and agent knowledge/memory tools |
 | Release | Not started | Development binary builds and tests | `.app` packaging, signing, entitlements, and notarization |
@@ -26,9 +26,10 @@ The application manages durable project/session metadata and model preferences.
 Its Model Manager downloads, validates, and deletes managed GGUF artifacts
 without blocking the UI. Local chat now lazily acquires the Rust DeepSeek Flash
 executor, streams generated text, supports cancellation and multi-turn role
-replay, and unloads model resources after the configured idle timeout. The
+replay, persists reasoning and answers while they stream, rehydrates selected
+sessions, and unloads model resources after the configured idle timeout. The
 current Rust graph supports DS4 compressed attention through 2K context; the sparse ratio-4 indexer,
-durable transcripts/KV checkpoints, HTTP service, and agent tools remain open.
+KV checkpoints, HTTP service, and agent tools remain open.
 
 ## Phase 0 — project and session shell
 
@@ -292,8 +293,8 @@ or KV frontier.
 
 ## Phase 3 — durable agent sessions
 
-Status: **partially open**. Project/session metadata rows exist; transcripts,
-model binding, and KV payload persistence are not implemented.
+Status: **partially implemented**. Project/session metadata and structured
+transcripts are durable; model binding and KV payload persistence remain open.
 
 Extend each metadata-only session with transcript and shared-checkpoint
 metadata:
@@ -308,10 +309,11 @@ Application Support/DS4Server.rfc1437.de/
     <ds4-cache-key>.kv
 ```
 
-- Add migrated message/transcript tables and an optional current-checkpoint key
-  to SQLite. Keep large engine-owned KV payloads only in the process-wide Phase
-  1 store, written with atomic replacement; do not introduce separate
-  agent-only or HTTP-only cache formats.
+- **Partially implemented:** migrated message tables persist user text,
+  reasoning state, and assistant output while generation streams. Add the
+  optional current-checkpoint key to SQLite. Keep large engine-owned KV
+  payloads only in the process-wide Phase 1 store, written with atomic
+  replacement; do not introduce separate agent-only or HTTP-only cache formats.
 - Record model identity, context size, rendered token history, title,
   timestamps, and working directory.
 - Restore compatible KV immediately. If KV is absent or incompatible, rebuild
@@ -329,13 +331,20 @@ the same conversation without prefill when its KV payload is compatible.
 ## Phase 4 — agent chat and tools
 
 Status: **basic local chat implemented**. The conversation area streams
-multi-turn DeepSeek Flash output and supports Stop; durable messages, tool
-turns, and the coding-agent runtime remain open.
+multi-turn DeepSeek Flash output, persists and rehydrates structured reasoning
+and answers, and supports Stop; tool turns and the coding-agent runtime remain
+open.
 
-1. **Partially implemented:** build the classic chat surface: transcript, reasoning disclosure, tool-call
-   cards, composer, queued input, stop button, prefill progress, and generation
-   statistics. Local turns must call the same session registry and KV path used
-   by the HTTP endpoint.
+Every chat feature must persist its semantic state and rehydrate it when a
+session is reopened in the same implementation slice. In-memory-only chat
+features are incomplete by definition; disclosure state and other purely
+ephemeral presentation preferences are the only exception.
+
+1. **Partially implemented:** build the classic chat surface. Transcript,
+   structured reasoning disclosure, composer, streamed output, and Stop are
+   complete; tool-call cards, queued input, prefill progress, and generation
+   statistics remain. Local turns must call the same session registry and KV
+   path used by the HTTP endpoint.
 2. Port the native agent turn loop from `ds4_agent.c`, including model-specific
    system prompts and DeepSeek DSML/GLM tool-call parsing.
 3. Implement the local tool set with the project directory as its boundary: