fix: bar blends with dapui bg, console capped at 5 rows, restart clears

Three refinements driven by the latest screenshot:

- TurboDebugBar highlight now links to Normal (was StatusLine). The
  StatusLine bg is usually darker than Normal in most colorschemes,
  which created a visible seam between our bar and the surrounding
  dapui pane headers (which inherit Normal/WinBar bg). Linking to
  Normal makes the bar blend so the overall UI reads as one unified
  surface rather than two mismatched strips.

- Console height now `min(5, 15% of avail)` with a 3-row absolute
  floor. Previously used `max(5, 15%)` which let Console balloon on
  tall terminals — misread the user's "minimum of 15% OR 5 rows"
  direction. Console is ancillary; caps at 5 to give the sidebar and
  source the vertical space they deserve.

- Clear-on-restart actually works now. Previous attempt deleted the
  entire console buffer on start/restart so dapui would create a fresh
  one — this worked on `(c)` start (new terminal opens) but broke on
  `(R)estart` because the adapter reuses the terminal channel, and
  deleting the buffer orphaned the channel (Console went unresponsive).
  New approach: KEEP the buffer, briefly toggle modifiable=true, and
  call nvim_buf_set_lines with empty content to wipe the scrollback.
  The PTY state and output stream stay intact; only the visible lines
  are gone. Default `clear_console_on_start = true` again.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lua/turbo-debug/config.lua

@@ -30,12 +30,8 @@ M.defaults = {
   -- it. Users can click/<CR> to expand manually.
   collapsed_scopes = { "Registers" },
 
-  -- Clear the Console pane on session start/restart. Disabled by default
-  -- because safe clearing is tricky: dapui's console buffer becomes a
-  -- terminal buffer once a session starts, and manipulating terminal
-  -- buffers mid-session destabilizes the adapter. Opt in explicitly if
-  -- you want it and accept the risk.
-  clear_console_on_start = false,
+  -- Clear the Console pane on session start/restart.
+  clear_console_on_start = true,
 
   -- modal keys (active only during debug mode, single-key)
   keys = {