fix: Hyperscript chip submit + comprehensive mascot documentation

Chips:
- Replace broken onclick with Hyperscript: `on click set #chat-input.value
  to '...' then trigger submit on #chat-form` — Hyperscript dispatches a
  native DOM submit event that HTMX intercepts correctly

Documentation (doc/28-AI-CHAT-AGENT.md — complete rewrite, ~544 lines):
- 18 sections covering full mascot feature reference
- Architecture diagram with end-to-end flow (11 steps)
- All 4 component files documented with code patterns
- query_cv tool: 11 section types in tables with examples
- Cross-section search mechanics explained
- Agent intelligence: 8 question-type strategies
- Suggested questions: chip-to-question mapping for both languages
- Design system: CV color tokens, typography, dark theme comparison
- Session management: OOB swap lifecycle
- Security: input/output sanitization, privacy rules
- Testing: 46 Playwright assertions across 25 test groups
- Configuration, dependencies, ADK Go concepts table

doc/00-GO-DOCUMENTATION-INDEX.md

@@ -36,12 +36,16 @@ This documentation covers the core Go systems that power the CV site, with a foc
    - Coverage gap explanations
    - Best practices and CI/CD integration
 
-5. **[AI Chat Agent](28-AI-CHAT-AGENT.md)** (~280 lines)
-   - ADK Go 1.0 integration architecture
-   - Agent definition with query_cv tool
-   - HTMX chat widget implementation
-   - Graceful degradation pattern
-   - Example conversations and security considerations
+5. **[AI Chat Agent — CV Assistant Mascot](28-AI-CHAT-AGENT.md)** (~500 lines)
+   - Complete mascot feature reference: architecture, components, intelligence
+   - ADK Go 1.0 integration with Gemini 2.5 Flash
+   - Agent definition with query_cv tool (11 section types, cross-section search)
+   - 8 question-type query strategies with instruction engineering
+   - HTMX + Hyperscript chat widget with suggested question chips
+   - Help modal with categorized example questions
+   - Session management (in-memory, OOB swap)
+   - Design system integration (CSS tokens, dark theme, responsive)
+   - Graceful degradation, security, and testing (46 Playwright assertions)
 
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