whatif: drop glide-path, compact form into 4 sections

The What-If form was a 14-field stack with always-visible hint
paragraphs — ~1500px scroll before "Run". The user is single-allocation
(100% stocks), so the glide-path knob was noise. Hardcoded
`static(1.0)` at the API layer; dropped `glide_path` from
`SimulateRequest` (extra field on persisted Scenario rows still
honoured for Cartesian sweeps).

Frontend reorganised into anchor numbers (NW / spend / horizon at
text-2xl), a Plan card (jurisdiction + leave-UK + strategy chips +
conditional Floor/Custom sub-card), a Returns card (3-chip segmented
control with inline manual %), and a folded Advanced section
(savings, MC paths, seed). Verbose hints moved into ⓘ popovers next
to each label. Two new primitives: SegmentedControl + InfoTip.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

fire_planner/api/simulate.py

@@ -25,7 +25,7 @@ from fire_planner.api.schemas import (
     SimulateRequest,
     SimulateResult,
 )
-from fire_planner.glide_path import get as get_glide
+from fire_planner.glide_path import static
 from fire_planner.ingest.wealthfolio_pg import create_wf_sync_engine_from_env
 from fire_planner.life_events import EventInput, events_to_cashflow_array
 from fire_planner.returns.bootstrap import block_bootstrap
@@ -119,7 +119,7 @@ def _project(req: SimulateRequest, paths: np.ndarray) -> tuple[SimulationResult,
         paths=paths,
         initial_portfolio=float(req.nw_seed_gbp),
         spending_target=float(req.spending_gbp),
-        glide=get_glide(req.glide_path),
+        glide=static(1.0),
         strategy=strategy,
         regime=build_regime_schedule(req.jurisdiction, req.leave_uk_year),
         horizon_years=req.horizon_years,