Add Oh My Pi agent integration

[louisgundelwein]

Closes #492

What

Adds omp / Oh My Pi as a first-class coding agent alongside the existing agent integrations:

• SkillAgent.omp display/config metadata, using the existing Pi mark fallback.
• Developer-tab install support for:
  • OMP extension at ~/.omp/agent/extensions/supacode/index.ts.
  • Supacode CLI skill at ~/.omp/agent/skills/supacode-cli/SKILL.md.
• Presence reporting over OSC 3008 for:
  • extension load → session_start
  • agent_start → busy
  • agent_end → idle + notification from last_assistant_message
  • session_shutdown → session_end + defensive idle
• Settings/sidebar metadata and tests so OMP appears in the coding-agents card and Active sidebar grouping.
• Coding-agents setup-card relevance cutoff bump so users who dismissed the old card are re-engaged for the expanded supported-agent lineup.

How

Oh My Pi is fork-compatible with Pi's extension API, but this PR keeps the OMP integration separate from Pi's installer/content instead of parameterizing Pi's existing implementation. That is intentional: OMP gets the fork-specific path/import/agent id, while existing Pi installs keep their current code path untouched.

Aspect	Pi	OMP
Config dir	.pi/agent	.omp/agent
Extension path	.pi/agent/extensions/supacode/index.ts	.omp/agent/extensions/supacode/index.ts
Emitted OSC agent id	pi	omp
Type import package	@mariozechner/pi-coding-agent	@oh-my-pi/pi-coding-agent
Icon	pi-mark	pi-mark fallback

The OMP installer mirrors the Pi ownership model:

• installs only into the managed supacode extension directory,
• uses /* supacode-managed-extension */ as the ownership marker,
• refuses to overwrite or remove user-authored content at the managed path,
• reports managed-but-drifted content as .outdated,
• removes stale empty managed directories on uninstall.

The extension stays inert unless SUPACODE_SURFACE_ID is present, so installing it outside a Supacode terminal has no effect. When SUPACODE_SOCKET_PATH is present, the OSC payload includes the local pid so Supacode's liveness sweep can reap crashed local agents; over SSH the pid is omitted because it is not meaningful to the local app.

Compared with closed PR #515, this keeps the low-risk parts and avoids the risky ones:

• Kept: fork-specific .omp/agent path, omp OSC id, @oh-my-pi/pi-coding-agent type import, installer/test coverage.
• Did not copy: global Pi installer/content parameterization, because this PR does not need to touch existing Pi behavior.
• Did not copy: custom omp-mark asset, because this PR intentionally uses the existing Pi mark fallback until an official/accepted asset is added.
• Did not copy: binary-availability gate, because this installer writes files only and does not need to execute omp; users can install the integration before installing/running the binary.

Tests

Added/updated coverage for:

• OmpSettingsInstallerTests
  • missing file → .notInstalled
  • user-authored file without marker is not treated as installed
  • invalid UTF-8 read failure does not masquerade as installed
  • install writes the expected OMP extension body under .omp/agent/extensions/supacode
  • install refuses to clobber user-authored content
  • stale managed content is overwritten by the canonical bundled extension
  • uninstall removes managed content and preserves user-authored content
  • OMP OSC lifecycle wire-string snippets are present
• AgentPresenceFeatureTests
  • OMP session_start registers the badge and pid
  • OMP session_end removes the local pid record
  • OMP busy sets activity
  • OMP idle clears activity while keeping the badge
• SidebarActiveClassificationTests
  • an idle OMP badge classifies the row as Active/agent
• CodingAgentsSidebarCardModeTests
  • OMP included in install-state dictionaries
  • cardRelevantSinceDate matches the OMP launch cutoff and re-engages previously dismissed users

Verification status

Ran locally:

• xcrun swiftc -parse SupacodeSettingsShared/BusinessLogic/OmpExtensionContent.swift SupacodeSettingsShared/BusinessLogic/OmpSettingsInstaller.swift SupacodeSettingsShared/Models/SkillAgent.swift SupacodeSettingsShared/BusinessLogic/CLISkillContent.swift SupacodeSettingsShared/BusinessLogic/CLISkillInstaller.swift SupacodeSettingsShared/BusinessLogic/AgentIntegrationFactory.swift supacode/Features/Settings/Views/DeveloperSettingsView.swift supacode/Features/AgentPresence/Views/CodingAgentsSidebarCardView.swift supacodeTests/OmpSettingsInstallerTests.swift supacodeTests/CodingAgentsSidebarCardModeTests.swift supacodeTests/AgentPresenceFeatureTests.swift supacodeTests/SidebarActiveClassificationTests.swift
• make format
• make lint
• git diff --check
• reviewer subagent: no Critical/Important findings before review follow-up

Review follow-up already included:

• Fixed the OMP OSC wire-string test expectation to match the installed TypeScript content (\\x1b, not doubled raw-string backslashes).
• Added a regression assertion that cardRelevantSinceDate matches the OMP launch cutoff.

Needs CI / maintainer-side validation:

• make build-app
• full make test
• targeted xcodebuild test for OmpSettingsInstallerTests

Blocked locally:

• make doctor / make build-app still fail because this machine lacks Xcode 26.3 with the macOS 26.2 SDK required for Zig 0.15.2/GhosttyKit.
• targeted xcodebuild test -project supacode.xcodeproj -scheme supacode -destination "platform=macOS" -only-testing:supacodeTests/OmpSettingsInstallerTests ... still stops before running tests: missing .build/ghostty/GhosttyKit.xcframework from the same Xcode/GhosttyKit prerequisite.

Contribution policy status

Aligned with CONTRIBUTING.md:

• Single linked issue: Closes #492.
• Issue state: Add pi / oh-my-pi as a coding agent #492 is open and unassigned.
• Issue readiness: Add pi / oh-my-pi as a coding agent #492 is marked ready.
• Commit authorship: commits are authored by Louis, with no AI-agent co-author trailers.
• Scope: one issue, one focused PR.

AI assistance disclosure

Prepared with AI assistance in the Supacode / Oh My Pi coding harness. Louis is the human author of record and accountable for the changes; no AI agent is listed as a git author or co-author.

[sbertix]

Thanks 🙇‍♂️