Fix Ctrl+hjkl navigation for herdr 0.7.0

[vlcinsky]

Summary

Fixes Ctrl+hjkl navigation for herdr 0.7.0, addressing the incompatibilities described in issue #1.

Problems Fixed

1. Pane ID format incompatibility

• Problem: Code was generating IDs as {workspace_id}-{index+1} (e.g., w3-1), but herdr 0.7.0 uses {workspace_id}:p{number} format (e.g., w3:p3)
• Solution: Use public_pane_numbers from session.json to generate correct public pane IDs in the new format

2. Focus API changed in 0.7.0

• Problem: Agent-based focus shim (report_agent → agent.focus → release_agent) no longer moves focus in herdr 0.7.0
• Solution: Use new pane.focus_direction RPC API added in herdr 0.7.0
• Backward compatibility: Falls back to computed approach if the new API is unavailable (for older herdr versions)

3. Key forwarding method changed in 0.7.0

• Problem: Using pane.send_text with raw control bytes caused keyboard protocol re-encoding issues
• Solution: Switch to pane.send_keys with key-combo strings ("ctrl+h", etc.) introduced in herdr 0.7.0 PR #613
• Benefit: Avoids keyboard protocol re-encoding issues and uses the proper API

4. Environment variable fallback

• Problem: Plugin relies on HERDR_ACTIVE_PANE_ID environment variable which herdr doesn't inject automatically in all cases
• Solution: Query herdr pane current API as fallback when environment variables are not set
• Benefit: More robust pane detection

5. LazyVim/distro keybinding conflicts

• Problem: LazyVim and similar distributions override Ctrl+{hjkl} keymaps after plugin setup
• Solution: Document the issue and provide a working configuration in README
• Benefit: Users can easily configure the plugin to work with LazyVim and similar distributions

Changes

Rust Binary (src/main.rs)

• pane_public_mapping(): Now uses public_pane_numbers to build correct {workspace}:p{n} IDs
• focus_pane_direction(): New function using pane.focus_direction API (herdr 0.7.0+)
• focus_adjacent(): Tries new API first, falls back to computed approach for compatibility
• send_ctrl_to_pane(): Switched from pane.send_text with raw bytes to pane.send_keys with key-combo strings

Lua Plugin (lua/herdr/navigator.lua)

• pane_id(): Added fallback to query herdr pane current API when env vars are missing

Documentation (README.md)

• Added LazyVim/distro compatibility section with working configuration
• Documented the keybinding conflict and solution

Testing

Tested locally with herdr 0.7.0 on macOS:

Binary navigation:

• ✅ herdr-navigator focus left/right/up/down - exit code 0
• ✅ herdr-navigator dispatch - correctly detects Neovim panes and forwards keys

Full integration:

• ✅ Ctrl+{hjkl} navigates within Neovim splits
• ✅ Ctrl+{hjkl} jumps from Neovim to adjacent herdr panes when at edge
• ✅ Ctrl+{hjkl} navigates between non-Neovim herdr panes
• ✅ Works with LazyVim using documented configuration

Compatibility

• ✅ Backward compatible with older herdr versions (falls back to old APIs)
• ✅ Forward compatible with herdr 0.7.0+ (uses new APIs when available)
• ✅ Works with LazyVim, NvChad, and other Neovim distributions (with documented config)

Closes #1