Implement Block 110 solver-backed Sketch dragging

[GideonBa]

Implements Block 110 of Interactive Sketcher MVP-8.

• adds stable semantic Endpoint, Midpoint, Center, Radius, Arc, Spline-control, and current Dimension-target handles
• deduplicates shared endpoint handles by persistent SketchPointId
• translates drag intent to transient Block-109 Coincident, Midpoint, Concentric, and Radial constraints without GUI-owned constraint mathematics
• keeps __gui.drag.pointer, __gui.drag.center, and zz.gui.drag.target outside published/committed topology
• strips augmented solver identity and rebuilds source-only solved topology by stable point id
• requires exact legacy materialization and topology re-migration before preview and again before commit
• coalesces move samples into one latest pending pointer
• synchronously flushes the exact final snapped release sample before commit
• publishes solved interaction scene, handles, solve status, and exact remaining DOF without mutating PartDocument
• refuses reference geometry and conflicting, non-convergent, invalid-reference, or incompatible fully constrained drag candidates
• restores the pre-drag scene/state on Esc, lost pointer capture, window deactivation, no-move handle click, and failed solve
• commits exactly one Drag sketch handle GuiDocumentSession transaction after source topology and constraint-system freshness checks
• restores normal Sketch selection/inference state after every drag lifecycle exit
• synchronizes Sketch toolbar QWidgetAction visibility so Finish Sketch remains fully hidden after workspace exit
• adds focused [gui][sketch-drag] and [integration][sketch-live-solve] proof
• updates the Interactive Sketcher, MVP, architecture, Sketch, solver, GUI, development, file-format, and README documentation to Block 111

Verification on Ubuntu 24.04 with Qt 6 and OCCT:

• complete GUI configuration succeeded
• complete build/dev-gui tree built successfully, including app, Core tests, Geometry tests, and GUI tests
• [gui][sketch-drag]: 138 assertions in 5 test cases passed
• [integration][sketch-live-solve]: 111 assertions in 4 test cases passed
• legacy Block 106 shell enters edits repeats and finishes a contextual Sketch proof passed three consecutive isolated runs, 48 assertions each
• complete ctest --test-dir build/dev-gui --output-on-failure: 891/891 tests passed
• Block 110 adds no persistence schema; handles, pointer samples, augmented drag topology/constraints, and live solve previews remain transient/derived
• temporary Block-110 verification workflows were removed from main before merge