feat: expand sudoku analysis and interoperability

public/README.md

@@ -8,33 +8,63 @@ release also runs independently from any static HTTPS host or local preview.
 ## Workspaces
 
 - **Play** — keyboard, mouse and touch entry; multi-cell selection; values,
-  corner/centre notes and colours; undo/redo; conflict highlighting; timer and
-  local progress; optional digit-completion counts and matching-digit
-  highlights.
+  corner/centre notes and colours; undo/redo; named savepoints, hypothesis
+  branches and read-only replay; conflict highlighting; timer and local
+  progress; optional digit-completion counts, matching-digit highlights and a
+  configurable non-constraining aid-mémoire.
 - **Set** — givens, metadata, regions and typed constraints; uniqueness checks
   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.
+  assessment; deterministic mining for a requested logical technique.
 - **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.
+- **Helpers** — generalized sum combinations with positional candidates and
+  manual eliminations; selected-cell and house candidate-link analysis; Killer
+  combinations, 45-rule residuals, and Kropki, sum-pair or inequality pairs.
 
 Classic grids and common variants share one bounded puzzle model: irregular
 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.
+5/10 sum-pair clues, inequalities, renban lines, palindromes, X-sums,
+skyscrapers, quadruples, maximum cells, anti-knight, anti-king and
+non-consecutive rules. Every local clue can also be required to be false for
+liar/Wrogn constructions. Fourteen original bundled examples demonstrate every
+supported constraint and are exact-search verified as unique.
+
+The board exposes real row/gridcell semantics and concise per-cell state to
+assistive technology, including candidates, notes, colours, conflicts and
+touching variant clues. Arrow keys never wrap; Home/End, Control/Command +
+Home/End and Page Up/Down provide row- and grid-level navigation. The same
+navigation model is available in the aid-mémoire scratch grid.
+
+## Interoperability and visual export
+
+The import dialog recognises compact grids, Sudoku Tools JSON/share fragments,
+raw or inline f-puzzles data, SudokuPad/CTC (SCL) data, and Penpa+ self-contained
+long links. It never follows a URL or resolves a server-side short ID. Imports
+are size/decompression bounded, report their detected source before applying,
+and stop with a list when a construct cannot be represented faithfully.
+
+SudokuPad compatibility currently preserves cells, givens and progress, notes,
+regions, metadata, solutions, Killer cages and supported global rules. Penpa+
+compatibility is intentionally narrower: square, unrotated Sudoku grids with
+givens/progress, thermometers and arrows. Visual-only lines, overlays, custom
+symbols and other unsupported geometry are reported rather than ignored.
+f-puzzles export likewise refuses false clues it cannot preserve.
+
+Export can produce a standalone SVG, a high-resolution PNG, or a single-page
+PDF entirely in the browser. Each visual uses the same trusted puzzle model and
+renders region boundaries, supported variant clues and givens; current values,
+notes and cell colours can be included or omitted with the progress switch.
 
 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.
+Technique practice performs a bounded, deterministic search and returns a
+puzzle only when its independently analysed solve path actually contains the
+requested technique.
 
 ## Privacy and storage
 
@@ -46,7 +76,8 @@ Exported files and share URLs contain the puzzle data you chose to include.
 
 SudokuPad short IDs identify server-hosted records and therefore cannot be
 resolved by this deliberately offline application. Embedded f-puzzles payloads
-are accepted without contacting their originating site.
+and user-provided Sudoku Tools JSON documents are accepted without contacting
+their originating site. Externally authored puzzle definitions are not bundled.
 
 ## Development
 
@@ -76,8 +107,8 @@ browser workflows and Toolbox contract before creating a deterministic
 
 The interaction ideas and published solving concepts explored by SudokuPad,
 SudokuWiki and the wider puzzle community informed the product requirements.
-No code, artwork, wording or proprietary puzzle data from those applications is
-included. Algorithms and explanations in this repository are independently
+No externally authored puzzle definitions, code, artwork or documentation text
+is bundled. Algorithms, UI, original examples and explanations are independently
 implemented from mathematical rules and public standards.
 
 ## Licence