fix(tui): anchor layout via dock so Input never moves (v0.2.1)

Reported during v0.2.0 mimir smoke: the Input pane bounces up/down
mid-turn and streamed tokens land at shifting screen positions. Cause
is the v0.2.0 compose order — `Static(id="thinking-current")` was
yielded between hint and Footer in the auto-stacked flow, so each
display=True/False toggle per thinking-run shifted Input + identity +
hint vertically. RichLog growth from streaming text also drifted Input
downward in the auto-layout.

Fix: dock the chrome to the screen edges via DEFAULT_CSS:
- thinking-current docks top under Header (grows/shrinks above RichLog,
  doesn't affect Input position).
- transcript (RichLog) gets `height: 1fr` — absorbs all layout reflows
  internally via its scroll viewport.
- prompt (Input), identity, hint all dock bottom — locked above Footer.

Compose order moves thinking-current to position 2 (right after Header)
so its dock-top placement is visually adjacent to where Textual lays it
out. Old position (between hint and Footer) would still work with the
dock CSS, but the proximity reads more clearly.

Screen-relative positions are now stable: Input is anchored to the
bottom-dock stack; RichLog's content scrolls inside its bounded
viewport regardless of how much thinking-current expands. Tokens land
at the same screen position each delta.

No public API change; pure layout fix. 209/209 tests GREEN; ruff clean.
v0.2.0 → v0.2.1 (patch).

Cannot directly verify in TTY from a non-interactive session; operator
verification needed in real terminal.

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "ratatoskr"
-version = "0.2.0"
+version = "0.2.1"
 description = "Worldtree Conversation API debug TUI — multi-pane observability dashboard"
 readme = "README.md"
 requires-python = ">=3.12"