feat(export): batch wafer-map PNG export from file list

- BatchExport worker + BatchExportController (threaded, busy flag)
- SourcePanel: Export Maps button → FolderDialog → batch export
  with progress/summary banner (dismissible)
- StreamControlPanel: name single export after loaded CSV + timestamp

CONTEXT.md

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+# Ubiquitous Language — ISenseCloud
+
+Glossary only. No implementation details. Terms verified against the C# original (`~/WA/temp_ui`) and the pyGUI redesign.
+
+## Terms
+
+**Wafer family** — the wafer type letter (A, B, C, D, E, F, P, X, Z) identifying sensor count and physical layout. Families group into layout classes: A/E/P (150C 48pt), B/C/D (250C 29pt), F (250C 22pt), X (150C 80pt).
+
+**Master (master file)** — the golden-reference CSV assigned per wafer family, used as the comparison baseline. Assigning a master is a per-family setting, not a layout choice. (C#: `btnAMaster`…`btnZMaster`; pyGUI: Settings tab master picker.)
+
+**Layout template** — a spreadsheet of sensor coordinates for a layout class, exported for external use. The C# "Layout" page buttons export these files; they do not change what is displayed. Not to be confused with a layout *selector*.
+
+**Edge–Center pair** — a fixed per-family mapping from each edge sensor to its radially-corresponding center sensor. Pairs involving a replaced sensor are skipped.
+
+**Edge–Center delta** — |edge temperature − paired center temperature| for one pair in one frame. The Edge-Center readout reports the min and max delta across pairs, with each pair's sensor numbers and temperatures.
+
+**Setpoint** — the target temperature the wafer run is trying to hold during the Set phase.
+
+**Margin** — the ± tolerance band around the color target used to color sensors/heatmap.
+
+**Sigma color (auto margin)** — coloring mode where the target is the frame average and the margin is the frame's σ, instead of the manual setpoint/margin.
+
+**Max range** — a temperature span used to find the largest set of sensors that fit within it (centered near the average/setpoint); sensors outside the set are flagged out-of-range.
+
+**Phase (Idle / Ramp / Set)** — the replay-time state of a frame: idle (flat, off-target), ramp (moving, colored by derivative sign), set (holding at setpoint).