feat(copilot): cross-platform PreToolUse hook via rtk hook (VS Code + Copilot CLI + Windows)

[jeziellopes]

Closes #593

What this adds

Cross-platform PreToolUse hook for GitHub Copilot (VS Code Copilot Chat + Copilot CLI) via rtk hook — a native Rust binary. No bash scripts, no jq, works on Windows natively.

How it works

rtk hook reads PreToolUse JSON from stdin, detects the agent format, responds appropriately:

VS Code Copilot Chat (updatedInput — transparent rewrite):

git status → rtk hook → updatedInput: "rtk git status"  (silent, no denial)

GitHub Copilot CLI (deny-with-suggestion — CLI ignores updatedInput today, copilot-cli#2013):

git status → rtk hook → deny: "Token savings: use `rtk git status` instead"
             Copilot reads reason → re-runs rtk git status

When Copilot CLI adds updatedInput support, only rtk hook needs a one-line change.

Also fixed

The old .github/hooks/rtk-rewrite.json had wrong key names (preToolUse → PreToolUse, bash/timeoutSec → command/timeout) that prevented it from loading in VS Code.

Measured gains (validated Copilot CLI session)

Command	Savings	Tokens saved
rtk cargo test	99.9%	15.8K
rtk cargo clippy --all-targets	93.3%	5.9K
rtk git diff HEAD~1	81.2%	2.6K
rtk gh pr list	67.0%	0.8K
Session total (24 commands)	83.5% avg	~23.3K

Files

File	Role
src/hook_cmd.rs	New rtk hook subcommand (13 unit tests)
.github/hooks/rtk-rewrite.json	Fixed key casing, points to rtk hook
hooks/copilot-rtk-rewrite.sh	Deleted — replaced by rtk hook
hooks/test-copilot-rtk-rewrite.sh	Rewritten to test rtk hook
hooks/copilot-rtk-awareness.md	Updated: VS Code row, both output paths
src/init.rs	Remove bash script checks, update status message
README.md	VS Code Copilot Chat support, Windows note
CHANGELOG.md	Updated unreleased entry

Testing

# Unit tests (13 tests)
cargo test hook_cmd

# Manual: Copilot CLI deny path
echo '{"toolName":"bash","toolArgs":"{\"command\":\"git status\"}"}' | rtk hook

# Manual: VS Code updatedInput path
echo '{"tool_name":"Bash","tool_input":{"command":"git status"}}' | rtk hook

# Verify rtk init --show
rtk init --show

[vrdons]

You should have to do windows support too, also his maybe works on vscode copilot integration. I'm planning to add many extensions to the VS Code chat integration.

[vrdons]

Also rewrite script should be automated. Maybe adding rust code should fix that

[jeziellopes]

@vrdons Great suggestions — this PR has been expanded to implement exactly what you described.

Rust binary instead of bash script ✅
Replaced hooks/copilot-rtk-rewrite.sh with rtk hook, a native Rust subcommand. No bash, no jq, no shell dependency. Works on Windows natively.

VS Code Copilot Chat support ✅
VS Code reads .github/hooks/*.json automatically (same dir, same format). I investigated the VS Code hooks docs and found that VS Code also supports updatedInput — which enables a transparent rewrite instead of a deny. So now rtk hook handles both agents differently:

• VS Code Copilot Chat → returns updatedInput (silent rewrite, no denial, no retry)
• GitHub Copilot CLI → returns permissionDecision: deny with suggestion (CLI ignores updatedInput today — tracked in copilot-cli#2013)

When Copilot CLI adds updatedInput support, only rtk hook needs a one-line change.

The old bash hook also had wrong key casing (preToolUse → should be PreToolUse, bash/timeoutSec → should be command/timeout). All fixed now.