Scratch: hosted shipping

Current Subgoal

Ship the hosted experiment path. Source hygiene is complete unless a fresh, concrete stale signature appears.

Removed unused solver hyperparams from src/repixelizer/params.py.
Removed stale tuning-campaign knobs from tools/solver_tuning_campaign.py.
Removed analysis / edge_map from the live phase-field solver path.
Simplified cleanup_pixels(...) to alpha snap plus zero heatmap.
Updated tests that still passed analysis into the solver/candidate-selection path.
Renamed the live observer/GUI flatness artifact from guidance to signal.
Fixed the signal payload rename bug where the observer still copied stale guidance.
Reworded docs/state from edge scout / solver guidance to diagnostic edge preview plus hierarchical flatness signal.
Updated GUI event listeners to the live lattice_inference_* events.
Reconciled config/solver_params.json with the documented shipping basin: grid=4.75, radius=0.215, blend=0.24, move=0.09, energy=1.4, peak=3.25.
Updated docs/spec.md so it describes the live explicit local-search solver and alpha snapping.

AST parse across src, scripts, tools, and tests: passed.
Targeted stale-string scan for solver params, cleanup hooks, guidance names, and solver-analysis call sites: clean.
Full source audit read 60 source files under src, scripts, tools, and tests; the only remaining analysis=analysis hit is the intentional RunResult diagnostic field.
Focused suite passed: tests/test_pipeline.py tests/test_gui.py tests/test_inference.py tests/test_phase_field.py.
Full suite passed: 89 passed.
tools/repixelizer_prepare_compaction.py: 19 ok, 2 expected warnings, 0 errors.

PhaseFieldSourceAnalysis intentionally remains as a diagnostic/GUI gauge for now. It does not steer the solver.
The remaining compaction warnings are expected: evidence ledger size, dirty worktree, and this scratch file existing.
Next real project move is shipping/commit hygiene and hosted deployment, not continuing this cleanup pass, unless a fresh scan finds a new concrete vestige.