fix(layout): restore [Docking] structure + per-window DockId references in bundled INI

Tier 2's commit e9654518 stripped the [Docking] data block and all
per-window DockId lines from layouts/default.ini based on the wrong
theory that HelloImgui would "auto-dock" panels via its central dockspace.
Empirically verified against tier2 branch HEAD (e9654518):

  manualslop_layout.ini after first launch: 1447 bytes (Docking block
  with DockSpace ID=0xAFC85805 + CentralNode=1, no DockNode children,
  no per-window DockId lines)

  User-visible result: empty dockspace with only the menu ribbon; 9
  default-visible panels are NOT rendered.

Compared with the user's working manualslop_layout.ini on master
(2150 bytes: full [Docking] hierarchy + 2 DockNode children + every
visible window has DockId=0x00000001,N or 0x00000002,N): panels render.

Root cause: the literal DockSpace ID in the bundled INI is matched by
imgui-bundle's HelloImgui against the dockspace it creates during the
session (ID computed deterministically from MainDockSpace name hash,
which is stable across sessions -- the SplitIds line in every
HelloImui-generated INI records 2949142533 = 0xAFC85805). The Phase 1
bundled INI had DockSpace ID=0xAFBEEF01 (one increment off the
correct ID) and Tier 2 stripped the entire docking structure on the
wrong theory that ids are session-incompatible. They aren't, as long as
the bundled INI's literal ID matches the runtime's computed ID.

This fix restores the docking structure in layouts/default.ini:

  - 8 [Window][...] entries (Project Settings, Files & Media, AI Settings,
    Theme, Operations Hub, Discussion Hub, Log Management, Diagnostics)
    each with Pos + Size + Collapsed=0 AND a DockId= line referencing
    0x00000001 (left column) or 0x00000002 (right column)
  - [Docking][Data] block with DockSpace ID=0xAFC85805 + 2 DockNode
    children (CentralNode=1 at 0x00000001 left, sibling at 0x00000002
    right)
  - HelloImGui_Misc block + SplitIds line
  - Comment block explaining the mechanism (replaces the misleading
    e9654518 "auto-dock layer" claim)
  - Omits Response (in _STALE_WINDOW_NAMES from src/gui_2.py:603-607)
    so _diag_layout_state does not emit a stale-name warning

The fix is the GOOD half of e9654518 -- the live-session
imgui.load_ini_settings_from_memory(src_text) apply after the copy
stays (it ensures the install takes effect on the current launch rather
than the next one). Only the INI content + the matching test
assertions change.

Tests:
  - _has_docking_block_with_docknodes (replaces _has_no_docking_block):
    asserts the bundled INI has [Docking][Data] with DockSpace AND
    >=1 DockNode ID= line
  - _every_window_has_dockid (new): asserts every [Window][...] header
    is followed by a DockId= line in its block
  - _has_no_stale_window_names (new): asserts no _STALE_WINDOW_NAMES
    entry is in the bundled INI

  17/17 tests pass (3 install + 2 reset_layout + 8 adjacent gui +
  4 commands).

Empirical verification:
  - delete cwd/manualslop_layout.ini
  - uv run python sloppy.py (no --enable-test-hooks; without this
    flag the app uses its regular GUI rendering pipeline)
  - log line: "[GUI] installed default layout: ...layouts/default.ini
    -> ...manualslop_layout.ini (and applied to live session)"
  - log line: "[GUI] visible-by-default windows: AI Settings,
    Diagnostics, Discussion Hub, Files & Media, Log Management,
    Operations Hub, Project Settings, Response, Theme"
  - saved manualslop_layout.ini post-launch: 3072 bytes with 2
    DockNodes, 8 [Window] entries (matches bundled INI minus runtime
    additions), 0 stale window names

tests/test_default_layout_install.py

@@ -98,8 +98,51 @@ def _has_window_with_collapsed_zero(text: str) -> bool:
  return False
 
 
-def _has_no_docking_block(text: str) -> bool:
- return "[Docking][Data]" not in text
+def _has_docking_block_with_docknodes(text: str) -> bool:
+ if "[Docking][Data]" not in text:
+  return False
+ if "DockSpace" not in text:
+  return False
+ docknode_count: int = 0
+ for line in text.splitlines():
+  if line.strip().startswith("DockNode") and "ID=" in line:
+   docknode_count += 1
+ return docknode_count >= 1
+
+
+def _every_window_has_dockid(text: str) -> bool:
+ lines: list[str] = text.splitlines()
+ blocks: dict[str, list[str]] = {}
+ for idx, line in enumerate(lines):
+  if line.startswith("[Window][") and line.rstrip().endswith("]"):
+   block: list[str] = []
+   for next_line in lines[idx + 1:]:
+    if next_line.startswith("[") and "][" in next_line:
+     break
+    block.append(next_line)
+   blocks[line] = block
+ if not blocks:
+  return False
+ has_dockid: bool = True
+ for header, block in blocks.items():
+  if not any("DockId=" in bl for bl in block):
+   has_dockid = False
+   break
+ return has_dockid
+
+
+def _has_no_stale_window_names(text: str) -> bool:
+ stale: set[str] = {
+  "Projects", "Files", "Screenshots", "Discussion History",
+  "Provider", "Message", "Response", "Tool Calls",
+  "Comms History", "System Prompts",
+ }
+ for line in text.splitlines():
+  if line.startswith("[Window][") and line.rstrip().endswith("]"):
+   name: str = line[len("[Window]["):-1]
+   if name in stale:
+    return False
+ return True
 
 
 def _workspace_for(tmp_path: Path, test_name: str) -> Path:
@@ -122,8 +165,14 @@ def _assert_installed_default(workspace: Path) -> None:
  assert _has_window_with_collapsed_zero(text), (
   f"installed INI has no [Window][...] entry; got first 400 chars: {text[:400]!r}"
  )
- assert _has_no_docking_block(text), (
-  f"installed INI should not contain a [Docking][Data] block (HelloImgui dockspace IDs are session-specific); got first 400 chars: {text[:400]!r}"
+ assert _has_docking_block_with_docknodes(text), (
+  f"installed INI missing [Docking][Data] block with DockSpace + >=1 DockNode children; got first 400 chars: {text[:400]!r}"
+ )
+ assert _every_window_has_dockid(text), (
+  f"installed INI does not have a DockId= line following every [Window][...] header; got first 400 chars: {text[:400]!r}"
+ )
+ assert _has_no_stale_window_names(text), (
+  f"installed INI contains a window name from _STALE_WINDOW_NAMES -- _diag_layout_state will emit a stale-name warning; got first 400 chars: {text[:400]!r}"
  )