Feature/spec kit add pi coding agent pullrequest

[mrGreazly]

Description

Add support for the Pi Coding Agent.

Main difference from PR #1596: Spec Kit commands are defined as prompts, not skills.
I belive it's more suitable to invoke these commands only manually and not letting agent to invoke them by itself. Also saw same approach for several other already supported agents.

Testing

• Tested locally with uv run specify --help
• Ran existing tests with uv sync && uv run pytest
• Tested with a sample project (if applicable)

AI Disclosure

• I did not use AI assistance for this contribution
• I did use AI assistance (describe below)

Changes made by pi coding agent (model - GPT 5.4). Gemini 3.1 was used for additional clarification and result checking.

Manually tested on simple project, passed all stages: constitution - specify - clarify - plan - tasks - analyze - implement

[Copilot]

Pull request overview

Adds first-class support for the Pi Coding Agent in Spec Kit, aligning Pi’s command location with its prompt-template model while keeping the rest of the agent ecosystem (skills install, context update scripts, and release packaging) consistent.

Changes:

• Register the pi agent in runtime/extension agent configs to use .pi/prompts with Markdown + $ARGUMENTS.
• Extend skills installation tests + agent consistency tests to cover Pi’s prompts/skills paths and release-script integration.
• Update docs and automation (context update scripts, release packaging, devcontainer setup) to include Pi.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/specify_cli/__init__.py	Adds pi to AGENT_CONFIG with .pi/ + prompts subdir and CLI requirement.
src/specify_cli/agents.py	Registers pi in CommandRegistrar.AGENT_CONFIGS as .pi/prompts markdown commands.
tests/test_extensions.py	Verifies pi command registrar mapping (.pi/prompts, markdown, $ARGUMENTS, .md).
tests/test_ai_skills.py	Adds Pi skills-dir resolution test and installs skills from .pi/prompts.
tests/test_agent_config_consistency.py	Adds cross-file consistency checks ensuring Pi is wired through configs + scripts + help text.
scripts/bash/update-agent-context.sh	Adds Pi to supported agent list and routes Pi updates through AGENTS.md.
scripts/powershell/update-agent-context.ps1	Adds Pi to ValidateSet and agent routing; updates help/usage text.
.github/workflows/scripts/create-release-packages.sh	Adds Pi to packaging matrix and outputs .pi/prompts templates.
.github/workflows/scripts/create-release-packages.ps1	Adds Pi to packaging matrix and outputs .pi/prompts templates.
.github/workflows/scripts/create-github-release.sh	Includes Pi template zips in the GitHub release artifact list.
.devcontainer/post-create.sh	Installs Pi Coding Agent npm package in devcontainer setup.
README.md	Documents Pi support and adds pi to CLI option lists.
AGENTS.md	Documents Pi’s directory conventions and CLI requirement.
docs/installation.md	Adds Pi to prerequisites and init examples.
docs/upgrade.md	Adds .pi/prompts/ to troubleshooting/upgrade guidance.

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[mnriem]

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