feat(copilot-cli): add GitHub Copilot CLI hooks integration

[ScottGuymer]

Summary

Implements #1588 — a new hindsight-integrations/copilot-cli/ package giving GitHub Copilot CLI persistent long-term memory via Hindsight hooks, modeled on the existing hindsight-integrations/cursor-cli/ package.

Hooks

Hook	Event	Purpose
session_start.py	sessionStart	Auto-recall — query memories using initialPrompt (or a project-context fallback query), inject as additionalContext
subagent_start.py	subagentStart	Auto-recall for subagents — every subagent Copilot CLI spawns (explore, task, research, code-review, rubber-duck, security-review, custom agents — not the built-in general-purpose agent, which never fires this hook) gets baseline project memory. Subagent payloads carry no per-invocation task text, so this always uses the fallback query.
agent_stop.py	agentStop	Auto-retain — reads the transcript, applies a configurable retainEveryNTurns cadence, POSTs to Hindsight (async); caches the transcript path for sessionEnd
session_end.py	sessionEnd	Final flush — forces a retain using the transcript path cached by the last agentStop, since sessionEnd's payload has no transcript path field of its own

Per-turn recall refresh (userPromptSubmitted/preToolUse) was deliberately skipped — those hooks don't support context injection per the official docs.

Installation

pip install hindsight-copilot-cli
hindsight-copilot-cli install --api-url https://api.hindsight.vectorize.io --api-token your-api-key

Also supports --scope repo for a team-shared .github/hooks/hindsight-copilot-cli.json registration (script install is still per-machine).

Testing

• 101 unit tests (mocked stdin/stdout/HTTP) covering all four hooks end-to-end, config layering, bank ID derivation, transcript parsing, and install/uninstall for both scopes.
• uv build && uv sync --frozen && uv run pytest tests -v all green (mirrors the new CI job).
• ruff check / ruff format --check clean against the shared repo ruff.toml.
• Verified hook I/O schemas against GitHub's official docs (not assumed) for sessionStart, subagentStart, agentStop, sessionEnd.

Other changes

• .github/workflows/test.yml — new test-copilot-cli-integration job + path filters, mirroring test-cursor-cli-integration.
• scripts/release-integration.sh / hindsight-dev/hindsight_dev/generate_changelog.py — registered copilot-cli for the release/changelog tooling.
• hindsight-docs/src/data/integrations.json + hindsight-docs/docs-integrations/copilot-cli.md — gallery/sidebar entry and docs page (passes check-integrations.mjs).
• hindsight-integrations/README.md — added a row for Copilot CLI, clarified the existing GitHub Copilot row is VS Code-specific.

Notes / known limitations

• The transcript file format is a best-effort port of the parsing logic from cursor-cli/claude-code — no live Copilot CLI transcript was available to validate the exact wire format against. Flagged in code comments and the README.
• uninstall's cleanup of the shared script directory uses an imperfect cwd-based heuristic to detect whether the other install scope is still registered — documented as an accepted v1 limitation (matches an equivalent limitation in cursor-cli).

Closes #1588