Add Qoder IDE installer target with global and local options

[liuwenji007]

This pull request adds first-class support for the Qoder agent to CodeGraph, enabling automatic detection and configuration via codegraph install. The installer now manages both global and project-local integration for Qoder, handling several agent-specific behaviors, and includes comprehensive tests to ensure correct setup, idempotency, and clean uninstallation. Documentation has been updated to reflect Qoder support throughout.

Qoder Agent Integration:

• Added Qoder as a supported agent in the installer registry (qoderTarget) and updated the TargetId type to include 'qoder'. [1] [2] [3]
• Implemented Qoder-specific installation logic:
  • Global install writes the MCP entry to Qoder's shared mcp.json in the platform config directory, ensuring idempotency and leaving sibling servers intact.
  • Local install writes both the shared MCP entry and a project-scoped .qoder/rules/codegraph.md rule file with Qoder-specific guidance and frontmatter, handling legacy migration and uninstall semantics.
• Comprehensive tests ensure correct file placement, argument handling (no --path or ${workspaceFolder}), idempotency, and proper uninstall behavior.

Documentation Updates:

• Updated all relevant sections of README.md to include Qoder as a supported agent, reflecting its presence in badges, install instructions, agent lists, and feature descriptions. [1] [2] [3] [4] [5] [6] [7]
• Added a detailed entry to the CHANGELOG.md describing the Qoder integration, agent-specific behaviors, and migration/compatibility notes.

Code Maintenance:

• Refactored the instructions template to centralize the CodeGraph guidance body for easier reuse and to clarify agent-specific customization. [1] [2]Supports --location=global (writes MCP entry to Qoder's shared mcp.json under ~/Library/Application Support/Qoder/SharedClientCache/) and --location=local (superset: additionally writes a project-scoped .qoder/rules/codegraph.md rule file with trigger: always_on frontmatter).

Key design decisions:

• Rule file at .qoder/rules/codegraph.md (higher precedence than AGENTS.md, filename codegraph fully owns — no marker fence needed)
• Qoder-specific playbook inlined (not the minimal shared block) because Qoder's client consumes MCP initialize.instructions weakly
• No --path argument: relies on MCP roots/list handshake instead of workspaceFolder substitution (older Qoder builds don't expand it)
• macOS absolute command resolution via login shell (same as Antigravity — handles stripped PATH from Dock/launchd)
• Self-heals legacy AGENTS.md CodeGraph fence on upgrade
• Atomic writes via atomicWriteFileSync for crash safety
• Local uninstall preserves shared MCP entry (cross-project safe)

Includes 10 test cases covering install/uninstall/idempotency/ self-heal/printConfig/detect across both locations.