Dashboard: editor graphics, new arithmetic/postselection blocks, displays, live update, All functions #342

Dashboard (Streamlit, offline) in tools/dashboard/. Continues Dense-Evolution-Discovery#235 (kept there as the trace). One PR per point, each reviewed before merge.

1. Editor graphics

• Wires as horizontal lines, 50 px apart; columns every 50 px
• Gates as 40×40 boxes with the standard symbol; control ● and target ⊕ joined by a vertical line; SWAP as ×
• Palette in groups of 2 columns, 2 px between boxes, 24 px between groups, group label above
• Measures studied in Quirk (Apache-2.0, src/Config.js, src/ui/DisplayedToolbox.js, src/ui/DisplayedCircuit.js), reimplemented; no link, import or export to Quirk

2. New engine operations in the editor

• Arithmetic blocks on registers: add_registers, subtract_registers, add_constant, comparisons, modular functions up to power_mod (Reversible arithmetic, point 1 of #336: addition and subtraction #337–Reversible arithmetic, point 3 of #336: modular arithmetic #339)
• Postselection block (Postselection, point 4 of #336 #340)
• Run them between gate segments in the Dashboard

3. Displays inside the circuit

• Bloch and probability markers per column from the state at that column (sota_views.step_states)

4. Live update

• Re-run the circuit on every edit

5. "All functions" section (engine_explorer.py)

• circuit_to_energy_fn, run_qiskit_circuit: first argument against their signatures
• pauli_expectation: example input
• from_pennylane, run_pennylane_circuit: need pennylane-qiskit
• continuous_dissipative_evolve, continuous_pulse_evolve, noise_model_from_qiskit_backend: decide on inputs
• AppTest: run every function, no exception

Estimate

About 45–65k tokens in total: 1) 8–12k, 2) 10–15k, 3) 10–15k, 4) 3–5k, 5) 8–12k, plus 3–5k of CI per PR.