Add terminal tab to capsule detail page and fix envd process lookup bugs

- Add multi-session Terminal tab with xterm.js (session tabs, close, reconnect)
- Keep terminal mounted across tab switches to preserve sessions
- Persist active tab in URL (?tab=terminal) so refresh stays on terminal
- Buffer keystrokes (50ms) to reduce per-character RPC overhead
- Add WebSocket auth via ?token= query param for browser WS connections
- Enable ws:true in Vite dev proxy for WebSocket support

envd fixes (pre-existing bugs exposed by multi-session terminals):
- Fix getProcess tag Range: inverted return values caused early stop when
  multiple tagged processes existed, making SendInput fail with "not found"
- Fix multiplexer deadlock: blocking send to cancelled fork's unbuffered
  channel prevented process cleanup. Now uses buffered channels (cap 64)
  with non-blocking fallback

frontend/pnpm-lock.yaml

@@ -8,6 +8,15 @@ importers:
 
   .:
     dependencies:
+      '@xterm/addon-fit':
+        specifier: ^0.11.0
+        version: 0.11.0
+      '@xterm/addon-web-links':
+        specifier: ^0.12.0
+        version: 0.12.0
+      '@xterm/xterm':
+        specifier: ^6.0.0
+        version: 6.0.0
       chart.js:
         specifier: ^4.5.1
         version: 4.5.1
@@ -534,6 +543,15 @@ packages:
     resolution: {integrity: sha512-S29BOBPJSFUiblEl6RzPPjJt6w25A6XsBqRVDt53tA/tlL8q7ceQNZHTjPeONt/3S7KRI4quk+yP9jK2WjBiPQ==}
     engines: {node: ^18.18.0 || ^20.9.0 || >=21.1.0}
 
+  '@xterm/addon-fit@0.11.0':
+    resolution: {integrity: sha512-jYcgT6xtVYhnhgxh3QgYDnnNMYTcf8ElbxxFzX0IZo+vabQqSPAjC3c1wJrKB5E19VwQei89QCiZZP86DCPF7g==}
+
+  '@xterm/addon-web-links@0.12.0':
+    resolution: {integrity: sha512-4Smom3RPyVp7ZMYOYDoC/9eGJJJqYhnPLGGqJ6wOBfB8VxPViJNSKdgRYb8NpaM6YSelEKbA2SStD7lGyqaobw==}
+
+  '@xterm/xterm@6.0.0':
+    resolution: {integrity: sha512-TQwDdQGtwwDt+2cgKDLn0IRaSxYu1tSUjgKarSDkUM0ZNiSRXFpjxEsvc/Zgc5kq5omJ+V0a8/kIM2WD3sMOYg==}
+
   acorn@8.16.0:
     resolution: {integrity: sha512-UVJyE9MttOsBQIDKw1skb9nAwQuR5wuGD3+82K6JgJlm/Y+KI92oNsMNGZCYdDsVtRHSak0pcV5Dno5+4jh9sw==}
     engines: {node: '>=0.4.0'}
@@ -1197,6 +1215,12 @@ snapshots:
 
   '@typescript-eslint/types@8.57.1': {}
 
+  '@xterm/addon-fit@0.11.0': {}
+
+  '@xterm/addon-web-links@0.12.0': {}
+
+  '@xterm/xterm@6.0.0': {}
+
   acorn@8.16.0: {}
 
   aria-query@5.3.1: {}