feat: dashboard + docs updates for native analysis

[melagiri]

Context

Part of the Native Analysis via Claude Code Hooks feature (Phase 12, v4.8.0).
Plan: docs/plans/2026-03-28-native-analysis-hooks.md

Issue 6 of 6 — Depends on #240 (insights command). Can be done in parallel with #241 and #242.

Dashboard Changes

Updated LlmNudgeBanner

Claude Code hook as primary CTA, API key as secondary:

Get AI-powered insights

Using Claude Code?
Run `code-insights install-hook` to analyze sessions
automatically with your Claude subscription.
No API key needed.

-------- or --------

Configure a provider for manual analysis:
Install Ollama for free local analysis, or set up
any provider in Settings.

[Configure AI Provider]

Analysis Provenance

On session detail, when provider = 'claude-code-native':

• Show "Analyzed via Claude Code · 24s" instead of "Analyzed with Anthropic / $0.04"
• No cost shown (tokens counted in Claude subscription)

No New Pages/Routes

Dashboard reads from the same insights, session_facets, and prompt_quality data regardless of how analysis was generated.

Documentation Updates

File	Change
CLAUDE.md	Add insights command to Commands section
docs/ARCHITECTURE.md	Add cli/src/analysis/ to repo structure, runner interface
docs/ROADMAP.md	Add Phase 12, version milestone v4.8.0
docs/PRODUCT.md	Add native analysis to features, update LLM section
docs/DEVELOPMENT.md	Add hook testing notes
README.md	Update features, add hook install to quickstart

Acceptance Criteria

• LlmNudgeBanner shows Claude Code hook as primary CTA
• AnalysisCostLine shows "Analyzed via Claude Code" for native provider
• No cost displayed for native-analyzed sessions
• CLAUDE.md updated with insights command
• ARCHITECTURE.md updated with cli/src/analysis/ directory
• ROADMAP.md includes Phase 12 + v4.8.0 milestone
• PRODUCT.md describes native analysis feature
• README.md quickstart includes install-hook