tui(browser): o opens highlighted POU in $EDITOR (or VS Code)

o on a POU row spawns $EDITOR (defaulting to 'code') with the
absolute path. detached + stdio:'ignore' + unref so the editor's
lifetime is independent of the TUI; shell:true so PATH lookup works
on Windows where 'code' is a .cmd shim.

Ignored on device rows (no abs_path).

src/tui/browser/Browser.tsx

@@ -11,6 +11,7 @@ export interface BrowserProps {
   writeSelection: (s: Selection) => void;
   onQuit: () => void;
   onRescan?: () => void;
+  onOpenInEditor?: (absPath: string) => void;
 }
 
 interface FlatRow {
@@ -32,7 +33,7 @@ function flatten(project: Project, expanded: Set<string>): FlatRow[] {
   return rows;
 }
 
-export function Browser({ project, readPou, writeSelection, onQuit, onRescan }: BrowserProps): React.ReactElement {
+export function Browser({ project, readPou, writeSelection, onQuit, onRescan, onOpenInEditor }: BrowserProps): React.ReactElement {
   const [expanded, setExpanded] = React.useState<Set<string>>(new Set());
   const [cursorIdx, setCursorIdx] = React.useState(0);
   const [text, setText] = React.useState<string | null>(null);
@@ -75,6 +76,9 @@ export function Browser({ project, readPou, writeSelection, onQuit, onRescan }:
     }
     if (input === 'q') return onQuit();
     if (input === 'r' && onRescan) return onRescan();
+    if (input === 'o' && onOpenInEditor && cursor?.kind === 'pou' && cursor.pou) {
+      return onOpenInEditor(cursor.pou.absPath);
+    }
     if (input === 'j' || key.downArrow) {
       setCursorIdx((i) => Math.min(i + 1, rows.length - 1));
     } else if (input === 'k' || key.upArrow) {
@@ -118,7 +122,7 @@ export function Browser({ project, readPou, writeSelection, onQuit, onRescan }:
           <Viewer pou={cursor?.pou ?? null} text={text} scrollTop={scrollTop} visibleRows={20} />
         </Box>
       </Box>
-      <Text>j/k nav  l expand  h collapse  r rescan  ? help  q quit</Text>
+      <Text>j/k nav  l expand  h collapse  o open  r rescan  ? help  q quit</Text>
     </Box>
   );
 }
@@ -131,6 +135,7 @@ function HelpOverlay(): React.ReactElement {
       <Text>  k / ↑     move cursor up</Text>
       <Text>  l / →     expand device</Text>
       <Text>  h / ←     collapse device</Text>
+      <Text>  o         open highlighted POU in $EDITOR (or VS Code)</Text>
       <Text>  r         re-scan mcp-mirror/</Text>
       <Text>  ?         toggle this help</Text>
       <Text>  Esc       close help</Text>

src/tui/index.tsx

@@ -1,6 +1,7 @@
 import React from 'react';
 import { render } from 'ink';
 import * as fs from 'fs/promises';
+import { spawn } from 'child_process';
 import { Approve, Decision } from './approve/Approve.js';
 import { Browser } from './browser/Browser.js';
 import { walk } from './shared/scan.js';
@@ -51,6 +52,15 @@ async function runBrowser(maybeRoot: string | undefined): Promise<number> {
       resolve(0);
     };
     const readPou = (pou: { absPath: string }) => fs.readFile(pou.absPath, 'utf8');
+    const onOpenInEditor = (absPath: string) => {
+      const editor = process.env.EDITOR || 'code';
+      try {
+        const child = spawn(editor, [absPath], { stdio: 'ignore', detached: true, shell: true });
+        child.unref();
+      } catch (err) {
+        process.stderr.write(`phobiCS-tui: open-in-editor failed: ${(err as Error).message}\n`);
+      }
+    };
     const onRescan = async () => {
       try {
         const next = await walk(root);
@@ -61,6 +71,7 @@ async function runBrowser(maybeRoot: string | undefined): Promise<number> {
             writeSelection={onWriteSelection}
             onQuit={onQuit}
             onRescan={onRescan}
+            onOpenInEditor={onOpenInEditor}
           />
         );
       } catch (err) {
@@ -74,6 +85,7 @@ async function runBrowser(maybeRoot: string | undefined): Promise<number> {
         writeSelection={onWriteSelection}
         onQuit={onQuit}
         onRescan={onRescan}
+        onOpenInEditor={onOpenInEditor}
       />
     );
   });

tests/tui/Browser.test.tsx

@@ -99,6 +99,44 @@ describe('<Browser>', () => {
     expect(lastFrame()).not.toContain('Keybindings');
   });
 
+  it('calls onOpenInEditor on o with the highlighted POU absPath', async () => {
+    const onOpenInEditor = vi.fn();
+    const { stdin } = render(
+      <Browser
+        project={project}
+        readPou={async () => ''}
+        writeSelection={() => {}}
+        onQuit={() => {}}
+        onOpenInEditor={onOpenInEditor}
+      />
+    );
+    await flush();
+    stdin.write('l');
+    await flush();
+    stdin.write('j');
+    await flush();
+    stdin.write('o');
+    await flush();
+    expect(onOpenInEditor).toHaveBeenCalledWith('/abs/PLC_PRG.st');
+  });
+
+  it('does not call onOpenInEditor when cursor is on a device row', async () => {
+    const onOpenInEditor = vi.fn();
+    const { stdin } = render(
+      <Browser
+        project={project}
+        readPou={async () => ''}
+        writeSelection={() => {}}
+        onQuit={() => {}}
+        onOpenInEditor={onOpenInEditor}
+      />
+    );
+    await flush();
+    stdin.write('o');
+    await flush();
+    expect(onOpenInEditor).not.toHaveBeenCalled();
+  });
+
   it('calls onRescan on r', async () => {
     const onRescan = vi.fn();
     const { stdin } = render(