feat: add project-theme plugin for per-project theme settings

plugins/project-theme/README.md

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+# Project Theme Plugin
+
+Applies per-project theme settings from `.claude/settings.json` on session start.
+
+## Problem
+
+When working on multiple projects simultaneously, all Claude Code sessions look identical. You have to manually run `/theme` each time you switch projects.
+
+## Solution
+
+This plugin reads theme settings from your project's `.claude/settings.json` and automatically applies them when the session starts.
+
+## Installation
+
+```bash
+/plugin install project-theme
+```
+
+Or for development:
+
+```bash
+claude --plugin-dir /path/to/project-theme
+```
+
+## Usage
+
+Add a `theme` or `color` key to your project's `.claude/settings.json`:
+
+```json
+{
+  "theme": "pink"
+}
+```
+
+Or use `.claude/settings.local.json` for local overrides:
+
+```json
+{
+  "theme": "dark"
+}
+```
+
+## Supported Values
+
+Any theme name supported by Claude Code's `/theme` command:
+
+- `dark` (default)
+- `light`
+- `light-ansi`
+- `dark-ansi`
+- `pink`
+- `blue`
+- `green`
+- `orange`
+- `purple`
+- `red`
+- `yellow`
+- Custom theme names from `~/.claude/themes/`
+
+## Priority
+
+Settings are loaded in this order (last wins):
+
+1. `.claude/settings.json` (project)
+2. `.claude/settings.local.json` (local override)
+
+## Example Workflow
+
+1. Create a project:
+   ```bash
+   mkdir my-project && cd my-project
+   mkdir -p .claude
+   echo '{"theme": "pink"}' > .claude/settings.json
+   ```
+
+2. Start Claude Code:
+   ```bash
+   claude
+   ```
+
+3. The pink theme is automatically applied!
+
+## How It Works
+
+The plugin uses a `SessionStart` hook that:
+
+1. Reads `.claude/settings.json` or `.claude/settings.local.json`
+2. Extracts the `theme` or `color` value
+3. Outputs a theme command that Claude Code processes
+
+## Limitations
+
+- Requires Claude Code 2.1.119+ (when `/config` settings persistence was added)
+- Theme is applied at session start; changing the file requires restarting
+- The hook reads files using basic grep; complex JSON with nested objects may not parse correctly
+
+## Contributing
+
+Contributions welcome! Areas for improvement:
+
+- Support JSON parsing for complex settings files
+- Add OSC terminal background color support
+- Watch for file changes and hot-reload themes
+- Support theme inheritance from parent directories
+
+## License
+
+MIT

plugins/project-theme/examples/.claude/settings.json

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+{
+  "theme": "pink"
+}

plugins/project-theme/hooks/apply-theme.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+# Apply per-project theme from .claude/settings.json
+# Usage: Add "theme": "pink" or "color": "blue" to your project's .claude/settings.json
+
+SETTINGS_FILE=".claude/settings.json"
+SETTINGS_LOCAL_FILE=".claude/settings.local.json"
+
+# Extract theme from JSON file using jq if available, else fallback to grep
+extract_theme() {
+  local file="$1"
+  if [[ ! -f "$file" ]]; then
+    return
+  fi
+
+  if command -v jq &>/dev/null; then
+    # Use jq for proper JSON parsing
+    jq -r '.theme // .color // empty' "$file" 2>/dev/null || true
+  else
+    # Fallback to grep for simple cases
+    grep -o '"\(theme\|color\)"\s*:\s*"[^"]*"' "$file" 2>/dev/null | head -1 | sed 's/.*"\([^"]*\)"$/\1/' || true
+  fi
+}
+
+# Check for theme in settings files (local takes precedence)
+THEME=""
+
+if [[ -f "$SETTINGS_LOCAL_FILE" ]]; then
+  THEME=$(extract_theme "$SETTINGS_LOCAL_FILE")
+fi
+
+if [[ -z "$THEME" && -f "$SETTINGS_FILE" ]]; then
+  THEME=$(extract_theme "$SETTINGS_FILE")
+fi
+
+if [[ -n "$THEME" ]]; then
+  echo "Applying project theme: $THEME"
+  # Output JSON command for Claude Code to process
+  echo "{\"type\": \"theme\", \"theme\": \"$THEME\"}"
+fi
+
+exit 0

plugins/project-theme/plugin.json

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+{
+  "name": "project-theme",
+  "version": "0.1.0",
+  "description": "Applies per-project theme settings from .claude/settings.json",
+  "author": "12britz",
+  "hooks": [
+    {
+      "event": "SessionStart",
+      "script": "hooks/apply-theme.sh",
+      "description": "Apply project-specific theme on session start"
+    }
+  ]
+}