feat: v1.3.0 — plan-first workflow, OpenRouter provider, enhanced prompt engine

Major changes:
- Plan-first workflow: AI generates structured plan before code, with
  plan review card (Modify Plan / Start Coding / Skip to Code)
- Post-coding UX: Preview + Request Modifications buttons after code gen
- OpenRouter integration: 4th AI provider with 20+ model support
- Enhanced prompt engine: 9 strategies, 11+ intent patterns, modular
- PLAN MODE system prompt block in all 4 services
- Fixed stale React closure in approveAndGenerate with isApproval flag
- Fixed canvas auto-opening during plan phase with wasIdle gate
- Updated README, CHANGELOG, .env.example, version bump to 1.3.0

CHANGELOG.md

@@ -0,0 +1,115 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [1.3.0] - 2025-03-18
+
+### Added
+- **OpenRouter Integration** — 4th AI provider with API key auth, 20+ model support
+  - New `lib/services/openrouter.ts` streaming service
+  - Provider selector in AI Assist: Qwen, Ollama, Z.AI, OpenRouter
+  - Default model: `google/gemini-2.0-flash-exp:free`
+  - Custom model selector with popular free/paid model presets
+  - Settings panel: API key input with validation and model picker
+- **Plan-First Workflow** — AI now generates a structured plan before code
+  - PLAN MODE instructions injected into all 4 service system prompts
+  - Plan card UI with architecture, tech stack, files, and steps
+  - `parsePlanFromResponse()` extracts plans from AI markdown output
+  - `[PLAN]` tags hidden from displayed chat messages
+  - Three action buttons: **Modify Plan** / **Start Coding** / **Skip to Code**
+- **Post-Coding UX** — Preview + Request Modifications after code generation
+  - After "Start Coding" approval, AI generates code with `[PREVIEW]` tags
+  - Canvas opens automatically with renderable previews
+  - Two post-coding buttons: **Preview** (re-opens canvas) and **Request Modifications**
+  - `isApproval` flag prevents stale React closure bugs in approval flow
+- **Enhanced Prompt Engine** — New modular prompt enhancement system
+  - `lib/enhance-engine.ts` with 9 enhancement strategies
+  - Strategies: clarify, add-context, add-constraints, structure, add-examples, set-tone, expand, simplify, chain-of-thought
+  - Context-aware enhancement based on detected intent type
+  - 11+ intent detection patterns (coding, creative, analysis, etc.)
+  - Smart strategy selection per intent for optimal prompt refinement
+- **Streaming Plan Mode** — Real-time plan parsing during AI response
+  - `wasIdle` flag captures initial request phase before state updates
+  - Canvas display suppressed during plan generation, enabled after approval
+  - Post-stream routing: plan card for initial requests, preview for approvals
+  - Tab `showCanvas` state gated by plan phase
+
+### Changed
+- **AIAssist.tsx** — Major refactor for plan-first flow
+  - `handleSendMessage` now accepts `isApproval` parameter to prevent stale closures
+  - `approveAndGenerate()` passes `isApproval=true` to bypass idle detection
+  - `assistStep` state machine: `idle -> plan -> generating -> preview`
+  - `parseStreamingContent()` filters `[PLAN]` tags from displayed output
+- **PromptEnhancer.tsx** — Rebuilt with modular enhance engine
+  - Moved enhancement logic to `lib/enhance-engine.ts`
+  - Added expand, simplify, and chain-of-thought strategies
+  - Improved intent detection and strategy mapping
+- **SettingsPanel.tsx** — Added OpenRouter provider configuration
+  - API key input with validation
+  - Model selector with preset dropdown
+  - Provider-specific endpoint display
+- **model-adapter.ts** — Extended with OpenRouter provider support
+  - New adapter mapping for OpenRouter service
+  - Unified interface across all 4 providers
+- **translations.ts** — Added i18n keys for plan mode, OpenRouter, post-coding actions
+  - Keys: `modifyPlan`, `startCoding`, `skipToCode`, `requestModifications`
+  - OpenRouter provider labels and descriptions
+  - English, Russian, Hebrew translations updated
+- **store.ts** — Added `selectedProvider` state for multi-provider selection
+- **types/index.ts** — Added `PreviewData` interface for typed canvas rendering
+- **adapter-instance.ts** — Registered OpenRouter in provider registry
+
+### Fixed
+- **Stale React closure** in `approveAndGenerate` — `setAssistStep("generating")` followed by `handleSendMessage()` read stale `assistStep` value. Fixed with explicit `isApproval` boolean parameter.
+- **Plan card reappearing after code generation** — Post-stream logic now correctly routes to `preview` mode after approval coding, not back to `plan` mode.
+- **Canvas auto-opening during plan phase** — `setShowCanvas(true)` in `onChunk` now gated by `!wasIdle` flag.
+- **i18n missing keys** — Added `syncComplete` for Hebrew, fixed double commas in multiple translation strings.
+
+### Technical Details
+- Files modified: 11 (960 insertions, 194 deletions)
+- Files added: 2 (`lib/enhance-engine.ts`, `lib/services/openrouter.ts`)
+- Total project lines: ~10,179 across core files
+- System prompt PLAN MODE block added to: `qwen-oauth.ts`, `ollama-cloud.ts`, `zai-plan.ts`, `openrouter.ts`
+
+## [1.2.0] - 2025-01-19
+
+### Added
+- **SEO Agent Behavior Fixes**
+  - SEO agent now stays locked and answers queries through an SEO lens
+  - Smart agent suggestions via `[SUGGEST_AGENT:xxx]` marker for clearly non-SEO tasks
+  - Visual suggestion banner with Switch/Dismiss buttons
+  - Prevented unwanted agent auto-switching mid-response
+- **z.ai API Validation**
+  - Real-time API key validation with 500ms debounce
+  - Inline status indicators:
+    - Checkmark with "Validated Xm ago" for valid keys
+    - Red X with error message for invalid keys
+    - Loading spinner during validation
+  - "Test Connection" button for manual re-validation
+  - Persistent validation cache (5 minutes) in localStorage
+
+### Changed
+- Updated Settings panel with improved UX for API key management
+- Enhanced agent selection behavior to prevent unintended switches
+
+## [1.1.0] - 2025-01-15
+
+### Added
+- GitHub integration for pushing AI-generated artifacts
+- XLSX export functionality for Google Ads campaigns
+- High-fidelity HTML report generation
+- OAuth token management for Qwen API
+
+## [1.0.0] - 2025-01-01
+
+### Added
+- Initial release of PromptArch
+- Multi-provider AI support (Qwen, Ollama, Z.AI)
+- Prompt Enhancer with 11+ intent patterns
+- PRD Generator with structured output
+- Action Plan generator with framework recommendations
+- Visual canvas for live code rendering
+- Multi-language support (English, Russian, Hebrew)