Editor: quick fixes, completion, navigation while typing, and split-pane drag (#109)

* feat(editor): Drag tabs and files between split panes

HTML5 drag and drop never reaches the webview while native file drop is
enabled, so tab, project-file and changelist drags did nothing. They now
run on pointer events:

- Drag an editor tab onto another pane, or onto a pane's edge to split it.
- Drag files from the Project view into an editor pane (center opens them
  there, an edge opens them in a new split).
- Drag files between changelists in the Commit view.
- "Drag-and-drop with Alt pressed only" applies to tabs and stripe buttons.

* fix(lsp): Deliver server settings and start servers on a supported JDK

- workspace/configuration answers a server's own section (basedpyright)
  from its settings block; basedpyright runs in "standard" mode and keeps
  auto search paths on, so `src/` layouts resolve from `tests/`.
- jdtls: formatting follows the editor indent, calls complete without
  guessed arguments, and JDK internals stay out of completion.
- `max-java` in a language server config picks an installed JDK no newer
  than that (kotlin-language-server fails on JDK 25).
- Server initialization may take up to 5 minutes (first Gradle import).
- `lsp_resend_diagnostics` re-emits stored diagnostics after a reload.
- Spelling only checks declared names (not called methods like
  `substring`) and accepts plurals of known software terms.

* feat(editor): Quick fixes, completion and navigation while typing

Quick fixes
- Errors get a red quick-fix bulb; Apply Quick Fix (⌥⇧↵) fixes the most
  severe problem at the caret, and the error hover offers the fix directly.
- Code generated by a code action is re-indented to the file's style.
- Python: Implement abstract methods (⌃I or the bulb) from the bases.
- Duplicate code actions are listed once.

Completion
- Overloads sharing a name, and a name importable from several modules,
  are no longer merged into one entry.
- Auto-import entries show the module they import from.
- Call snippets without a stop (`new ArrayList<>()`) leave the caret inside
  the parentheses with parameter info, or past them when nothing takes
  arguments; parameter info also opens after server call snippets.
- The selected item is resolved ahead of acceptance, so its auto-import
  is applied (rust-analyzer).

Navigation and diagnostics
- Language server requests wait for pending edits, so Go to Declaration
  right after typing answers for the current text; an empty answer right
  after an edit is retried while the server catches up.
- Diagnostics come back after a window reload; error underlines stay
  visible under typo / unused highlighting.
- Implementation gutter markers no longer refresh in a loop while the
  server reports progress.
- A missing alternative server no longer shows as a server error.

* chore(lint): Skip agent worktrees under .claude

* fix(editor): Skip cancelled LSP requests and limit generated-code reformat

- Requests cancelled while waiting for pending edits are not sent.
- Code generated by an action is reformatted per changed hunk, so an added
  import doesn't reformat the code between it and the generated lines.
- A long busy spell caused by a settle refresh re-runs it only once.
- Files dropped on a file row of another changelist move to that changelist.
- Python Implement methods: a nested class without bases ends the lookup,
  class bodies continue through unindented string lines, and
  `@abstractproperty` stubs become `@property`.
- Resend diagnostics goes through the host ops, and custom servers get
  `max_java`.

* fix(editor): Rank the exact type first in Java constructor completion

jdtls appends the call or body to filterText (`String(${0})`); matching
on the label instead lets typing `String` rank `String` above
`StringBuilder` and the other types sharing its sort text.

* fix(editor): List identical completion items once

kotlin-language-server repeats a class once per classpath entry declaring
it, so `String()` and `String` were listed three times each.

* fix(editor): Keep the internal cancellation message out of the UI text catalog

src/workbench/contributions.ts

@@ -379,6 +379,8 @@ export interface OpenOptions {
   preview?: boolean;
   /** Open to the side (split right). */
   side?: boolean;
+  /** Open in this editor pane, in a tab of its own even when another pane shows the file. */
+  pane?: string;
   focus?: boolean;
   /** Open in the text editor even when a file editor provider claims the file (SVG as text). */
   asText?: boolean;

src/workbench/toolwindows/ToolWindows.tsx

@@ -15,7 +15,7 @@ import { create } from "zustand";
 import { call, commands } from "@/platform/ipc";
 import { shortcutLabel } from "@/platform/keymap";
 import { useProject } from "@/platform/project";
-import { Icon, IconButton, Menu, showContextMenu, tooltipAttrs, type MenuItem, T } from "@/ui";
+import { dragRequiresAlt, Icon, IconButton, Menu, showContextMenu, tooltipAttrs, type MenuItem, T } from "@/ui";
 import { FOCUSABLE } from "@/ui/popupState";
 import { TabStripRegistry } from "@/ui/Tabs";
 import { useContributions, type ToolWindowAnchor, type ToolWindowContribution } from "../contributions";
@@ -303,7 +303,7 @@ function stripeDropAt(x: number, y: number): StripeDrop | null {
 }
 
 function startStripeDrag(e: PointerEvent<HTMLButtonElement>, id: string) {
-  if (e.button !== 0) return;
+  if (e.button !== 0 || (dragRequiresAlt() && !e.altKey)) return;
   const button = e.currentTarget;
   const start = { x: e.clientX, y: e.clientY };
   let ghost: HTMLElement | null = null;