chore(root): use PID

docs/history.md

@@ -0,0 +1,25 @@
+# Shell History Integration (`integration/history.go`)
+
+The `history` module provides the Ctrl+R fuzzy search functionality by reading the user's persistent shell command history.
+
+## Features
+
+- **Zsh Extended Support**: Specifically parses the `: <timestamp>;<command>` format common in Zsh.
+- **Lazy Loading**: Doesn't read the disk until the user actually requests history. This keeps startup time instantaneous.
+- **Fuzzy Search**: Integrated with the `fuzzyvn` search engine.
+- **Deduplication**: Automatically hides duplicate entries, showing only the most unique command variants.
+
+## Data Flow
+
+1. User presses `Ctrl+R`.
+2. `root` sets `mode = "history"`.
+3. `SearchHistory("")` is called.
+4. If `cache` is empty:
+   - Reads `~/.zsh_history`.
+   - Strips metadata using `;` delimiter.
+   - Populates a slice of commands.
+5. Search matches are sorted by the `fuzzyvn` engine.
+6. Suggestions are returned to the `overlay` for rendering.
+
+## Configuration
+It currently looks for `.zsh_history` in the user's home directory.