Add generic agent support for unsupported AI agents (bring your own agent)

[mnriem]

Summary

Users whose AI agent isn't yet supported by Spec Kit are currently they can't scaffold a project until a PR adds formal support for their agent.blocked

Proposal

Add a --ai generic option that works with a required --ai-commands-dir <path> flag, allowing users to specify where their agent reads commands from.

Example:

specify init my-project --ai generic --ai-commands-dir .myagent/commands/

This scaffolds the full SDD structure (specs, templates, scripts, memory) and places Markdown command files in the user-specified directory.

Design Decisions

• --ai-commands-dir is required when using --ai generic (errors if a default like .speckit/commands/ would be useless since no agent reads from thereomitted)
• --ai-commands-dir is rejected when used with any other agent
• Commands are generated as Markdown with $ARGUMENTS (compatible with 16 of 18 supported agents)
• No CLI tool check is performed for generic
• Release ZIPs use a placeholder directory (.speckit/commands/) that gets renamed to the user's path during init

Changes Required

• Add generic to AGENT_CONFIG in src/specify_cli/__init__.py
• Add --ai-commands-dir parameter to the init() command
• Update release packaging scripts (bash + PowerShell)
• Update GitHub release script
• Update agent context scripts
• Update README, CHANGELOG, AGENTS.md
• Version bump

[dhilipkumars]

Does this unblock this #1572 ? @@xswangme-lang

[dhilipkumars]

This is smart.