docs: refine Phase 2 — chat templates + reasoning parser + collapsible TUI thoughts section

plan.md

@@ -136,19 +136,37 @@ CREATE TABLE context_state (
 
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-## Phase 2 — Prompt Templating & Format Fix
+## Phase 2 — Prompt Templating & Reasoning-Aware TUI
 
-**Goal:** Fix model output. Swap raw prompt text for a configurable chat template so the model only returns the assistant response, not reasoning meta-text.
+**Goal:** Fix model output with proper chat templates. Parse reasoning/thoughts from the response and render them beautifully in the TUI — dimmed, collapsible, like OpenCode.
+
+### Chat Template Engine
 
 - [ ] `internal/llama/template.go` — chat template formatter:
   - ChatML: `<|im_start|>system\n...<|im_end|>\n<|im_start|>user\n...<|im_end|>\n<|im_start|>assistant\n`
   - Llama 3 instruct: `<|begin_of_text|><|start_header_id|>system<|end_header_id|>\n...<|eot_id|>`
+  - DeepSeek R1: with `...` support
   - Configurable via env `CHAT_TEMPLATE=chatml` (default)
 - [ ] Refactor `companion/promptbuilder.go` to output structured segments (system context, personality, relationship, conversation history, user message)
 - [ ] Let template.go wrap those segments in the chosen format
-- [ ] Strip system prompt of raw formatting headers — let template handle structure
 - [ ] Add `stop` tokens per template (`<|im_end|>`, `<|eot_id|>`)
-- [ ] **Test:** "hi" produces just "Hello!" not paragraphs of self-correction
+- [ ] **Test:** "hi" produces just the response, no meta-text
+
+### Reasoning Parser
+
+- [ ] `internal/agent/reasoning.go` — parse `...`, `...`, or custom tags from model output
+- [ ] Split response into `Reasoning` (thoughts) and `Content` (final answer)
+- [ ] Store both separately in the `messages` table
+- [ ] Feed only `Content` back into context window (reasoning is discarded after display)
+
+### TUI Enhancement
+
+- [ ] Render reasoning in a collapsible section:
+  - Header: "💭 (or `...`) with reasoning snippet
+  - On click/expand: show full reasoning in dimmed/italic style (`lipgloss.Color("#6B7280")`)
+- [ ] Render final answer in normal assistant style (green/bold)
+- [ ] Reasoning hidden by default, toggle with a keybinding (e.g., `tab`)
+- [ ] **Test:** Send a prompt that triggers reasoning, verify collapsible display
 
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