feat: add gameplay assists and variant generator

public/README.md

@@ -9,20 +9,32 @@ release also runs independently from any static HTTPS host or local preview.
 
 - **Play** — keyboard, mouse and touch entry; multi-cell selection; values,
   corner/centre notes and colours; undo/redo; conflict highlighting; timer and
-  local progress.
+  local progress; optional digit-completion counts and matching-digit
+  highlights.
 - **Set** — givens, metadata, regions and typed constraints; uniqueness checks
-  and seeded classic puzzle generation.
+  with overlap-safe cage replacement and selection-based cage removal.
+- **Generate** — seedable, bounded construction for classic and 12 variant
+  families; independent uniqueness verification and evidence-based difficulty
+  assessment.
 - **Solve** — exact solution counting plus an original human-style engine whose
   steps include structured evidence, placements and eliminations.
 - **Helpers** — Killer combinations and candidate-aware assignments, 45-rule
   residuals, and Kropki, XV or inequality relation pairs.
 
 Classic grids and common variants share one bounded puzzle model: irregular
-regions, diagonals, Killer cages, thermometers, arrows, Kropki and XV clues,
-inequalities, renban lines, palindromes, anti-knight, anti-king and
-non-consecutive rules. Import accepts compact grid strings, this project's JSON
-format, share fragments, and the common f-puzzles fields supported by the
-model. Unknown constraints are reported rather than silently discarded.
+regions, diagonals, Killer cages, thermometers, arrows, Kropki and numbered
+5/10 sum-pair clues, inequalities, renban lines, palindromes, anti-knight,
+anti-king and non-consecutive rules. Thirteen bundled, uniquely checked examples
+demonstrate every supported constraint. Import accepts compact grid strings,
+this project's JSON format, share fragments, and the common f-puzzles fields
+supported by the model. Unknown constraints are reported rather than silently
+discarded.
+
+Generation supports only size/variant combinations which pass the bounded
+construction checks. The requested difficulty controls clue-removal targets;
+the displayed 0–100 result is calculated afterwards from logical techniques,
+clue load and reproducible exact-search evidence. A timeout or node limit is
+reported as unknown and never promoted to a uniqueness or difficulty claim.
 
 ## Privacy and storage