chore: add repo assets, templates, and keyword optimization

- Banner SVG and social preview SVG (.github/assets/)
- Architecture and pipeline diagram SVGs for README
- Issue templates (bug, feature request, new skill)
- PR template with stitch-specific checklist
- README title rewritten for search discoverability
- package.json keywords expanded (google-stitch, model-context-protocol, etc.)
- Fixed SVG XML entities for GitHub rendering
- Added ._* to gitignore for macOS resource forks

Author: Gabi

.github/ISSUE_TEMPLATE/bug.md

@@ -0,0 +1,26 @@
+---
+name: Bug report
+about: Something broke or isn't working right
+title: "fix: "
+labels: bug
+---
+
+## What you expected
+
+## What actually happened
+
+## Which agent and version?
+
+e.g., Claude Code 1.x, Codex CLI, Cursor — and which skill triggered the issue
+
+## Steps to reproduce
+
+1.
+2.
+3.
+
+## Stitch MCP response (if relevant)
+
+```
+Paste error output or MCP response here
+```

.github/ISSUE_TEMPLATE/feature-request.md

@@ -0,0 +1,24 @@
+---
+name: Feature request
+about: Suggest a new skill, framework target, or workflow improvement
+title: "feat: "
+labels: enhancement
+---
+
+## What problem does this solve?
+
+## Which layer does it belong to?
+
+- [ ] Orchestrator (routing / coordination)
+- [ ] Brain (ideation / prompt engineering / specs)
+- [ ] MCP wrapper (new or improved Stitch API wrapper)
+- [ ] Conversion (new framework target)
+- [ ] Quality (a11y / animation / design system)
+
+## What would the skill do?
+
+Describe the workflow — what goes in, what comes out.
+
+## Alternatives you've considered
+
+Have you tried doing this with existing skills? What fell short?

.github/ISSUE_TEMPLATE/new-skill.md

@@ -0,0 +1,28 @@
+---
+name: New skill contribution
+about: Propose or submit a new skill for the plugin
+title: "feat: add skill — "
+labels: new-skill
+---
+
+## Skill name
+
+`stitch-*` prefix required for Stitch-related skills
+
+## What it does
+
+One sentence. What goes in, what comes out.
+
+## Which layer?
+
+Orchestrator / Brain / MCP wrapper / Conversion / Quality
+
+## SKILL.md included?
+
+- [ ] Yes — YAML frontmatter + markdown instructions
+- [ ] Examples directory with at least one real usage
+- [ ] Follows the skill anatomy in README
+
+## Why this doesn't already exist
+
+Which existing skill is closest, and what gap does this fill?