feat: add multi-tool integration scripts and converted agent files

Adds support for installing The Agency agents across 7 agentic coding
tools via two scripts:

scripts/convert.sh
  - Reads all 61 agents and converts them into tool-specific formats
  - Supports: Antigravity, Gemini CLI, OpenCode, Cursor, Aider, Windsurf
  - Shellcheck-clean, pure bash, no external deps
  - Run: ./scripts/convert.sh [--tool <name>]

scripts/install.sh
  - Interactive terminal UI with auto-detection of installed tools
  - Pre-selects detected tools, toggle by number or bulk commands
  - Falls back gracefully in CI / non-interactive mode
  - Cross-platform: Linux, macOS (bash 3.2+), Windows Git Bash / WSL
  - Run: ./scripts/install.sh [--tool <name>] [--no-interactive]

integrations/ (generated, committed for reference)
  - antigravity/   SKILL.md per agent (61 files)
  - gemini-cli/    SKILL.md per agent + gemini-extension.json
  - opencode/      .md agent files for .opencode/agent/
  - cursor/        .mdc rule files for .cursor/rules/
  - aider/         single CONVENTIONS.md (all agents combined)
  - windsurf/      single .windsurfrules (all agents combined)
  - claude-code/   README only (agents copied directly from repo root)
  - README.md      full usage + tool-specific instructions

README.md
  - Added Multi-Tool Integrations section with supported tools table,
    quick-start guide, per-tool expandable instructions, and updated
    roadmap marking integrations as complete

integrations/README.md

@@ -0,0 +1,118 @@
+# 🔌 Integrations
+
+This directory contains The Agency's 61 AI agents converted into formats
+compatible with popular agentic coding tools.
+
+## Supported Tools
+
+| Tool | Format | Directory |
+|------|--------|-----------|
+| [Claude Code](#claude-code) | `.md` with frontmatter | *(use repo directly)* |
+| [Antigravity](#antigravity) | `SKILL.md` per agent | `antigravity/` |
+| [Gemini CLI](#gemini-cli) | Extension + `SKILL.md` | `gemini-cli/` |
+| [Cursor](#cursor) | `.mdc` rules | `cursor/` |
+| [Aider](#aider) | `CONVENTIONS.md` | `aider/` |
+| [Windsurf](#windsurf) | `.windsurfrules` | `windsurf/` |
+
+## Quick Install
+
+```bash
+# Install for all detected tools automatically
+./scripts/install.sh
+
+# Install for a specific tool
+./scripts/install.sh --tool antigravity
+./scripts/install.sh --tool gemini-cli
+./scripts/install.sh --tool cursor
+./scripts/install.sh --tool aider
+./scripts/install.sh --tool windsurf
+./scripts/install.sh --tool claude-code
+```
+
+## Regenerating Integration Files
+
+If you add or modify agents, regenerate all integration files:
+
+```bash
+./scripts/convert.sh
+```
+
+---
+
+## Claude Code
+
+The Agency was originally designed for Claude Code. Agents work natively
+without conversion.
+
+```bash
+cp -r <category>/*.md ~/.claude/agents/
+# or install everything at once:
+./scripts/install.sh --tool claude-code
+```
+
+See [claude-code/README.md](claude-code/README.md) for details.
+
+---
+
+## Antigravity
+
+Skills are installed to `~/.gemini/antigravity/skills/`. Each agent becomes
+a separate skill prefixed with `agency-` to avoid naming conflicts.
+
+```bash
+./scripts/install.sh --tool antigravity
+```
+
+See [antigravity/README.md](antigravity/README.md) for details.
+
+---
+
+## Gemini CLI
+
+Agents are packaged as a Gemini CLI extension with individual skill files.
+The extension is installed to `~/.gemini/extensions/agency-agents/`.
+
+```bash
+./scripts/install.sh --tool gemini-cli
+```
+
+See [gemini-cli/README.md](gemini-cli/README.md) for details.
+
+---
+
+## Cursor
+
+Each agent becomes a `.mdc` rule file. Rules are project-scoped — run the
+installer from your project root.
+
+```bash
+cd /your/project && /path/to/agency-agents/scripts/install.sh --tool cursor
+```
+
+See [cursor/README.md](cursor/README.md) for details.
+
+---
+
+## Aider
+
+All agents are consolidated into a single `CONVENTIONS.md` file that Aider
+reads automatically when present in your project root.
+
+```bash
+cd /your/project && /path/to/agency-agents/scripts/install.sh --tool aider
+```
+
+See [aider/README.md](aider/README.md) for details.
+
+---
+
+## Windsurf
+
+All agents are consolidated into a single `.windsurfrules` file for your
+project root.
+
+```bash
+cd /your/project && /path/to/agency-agents/scripts/install.sh --tool windsurf
+```
+
+See [windsurf/README.md](windsurf/README.md) for details.