[Trosper3]

Summary

Instance strings are now read in a single pass that ignores whitespace around structure, reports bad input with a clear message and position, and can't be slowed down or crashed by large or deeply nested input. Every bad-input case now throws one exception type, SpadeParseException.

Stacked on #15. Only the last two commits belong to this PR.

Merge order

#11, #13, #15 and #16 are stacked. Merge them into main in this order:

0. ci: run the Redux Build System (rbs) report, soft for now #31: rbs CI report and dotnet format (the new base)
1. fix(collections): hash sets independently of element order #11 (for Equal sets hash differently, so sets of sets give wrong answers #9): set hashing; adds the test project the others use
2. fix(grammar): accept set edges in unorderedcross again #13 (for fix(grammar): unorderedcross rejects every edge since d7e982e #12): unorderedcross edges
3. fix(grammar): make is int, is set and is list check their type #15 (for is int and is set constraints don't check their type #10): is int / is set / is list type checks
4. feat(parser): read instance strings in one pass, with clear errors #16 (for Ignore whitespace that isn't part of a value #2, Clear parse errors #4, Parsing is slow on large input and crashes the process on deep nesting #7): one-pass instance reader and clear errors (this PR)
5. feat(collections): add multisets #17 (for Add multisets #1): multisets. Optional for the next release: no Redux definition uses it until Redux opts in.

After each merge, the next PR shows only its own commits. If one is squash-merged, I'll rebase the next one onto main before it's reviewed.

Releasing for Redux: publish a new version only after all four are merged. Redux's grammar fixes (ReduxISU/Redux#628, ReduxISU/Redux#629, ReduxISU/Redux#630) work with 0.1.2 and can land any time before the upgrade; only ReduxISU/Redux#630's test changes go in the same Redux PR that upgrades the SPADE package. Tracked in ReduxISU/Redux#627.

What changed

Commit 1, feat(parser): read instance strings in one pass (for #2 and #7, part of #4)

• New InstanceScanner replaces the substring-based reader in UtilCollection(string).
• Whitespace (Ignore whitespace that isn't part of a value #2): spaces, tabs and line breaks around { } ( ) , and at either end are skipped. Inside a value, whitespace next to [ ] ; : = is dropped, plain spaces are kept (New York), and a run with a tab or line break becomes one space (New\nYork reads as New York). These are the same rules Redux applies before parsing today, so that layer can be removed.
• Syntax errors (Clear parse errors #4): malformed input throws SpadeParseException with Position (from 1), Expected and Found, e.g. expected , or } at position 5, found end of input for {1,2. Nothing is guessed any more: {1,2 used to read as {1}, and {1,2}junk as {1,2}jun}.
• Time and depth (Parsing is slow on large input and crashes the process on deep nesting #7): parsing is linear in the input's length, and ToString builds its text in one buffer. Nesting is limited to 256 levels, and deeper input is rejected instead of overflowing the stack.
• New SpadeParseException (a FormatException).
• Docs: "Whitespace" and "Errors" sections in Documentation/InstanceString.md.

Commit 2, fix(grammar): report shape and constraint failures as SpadeParseException (for #4)

• A format such as (N,E) checks it got a list of exactly that many elements. A 3-element list used to be accepted with the extra element dropped. A set or value used to crash with InvalidOperationException.
• Constraint failures quote the constraint as written instead of PLACEHOLDER, e.g. Constraint E subset N unorderedcross N failed: {1,9} is not a member. Long values are shortened to keep messages short.
• subset on a plain value, and cross on anything that isn't a pair, fail the constraint instead of crashing.
• Docs: "Handling bad input" in Documentation/example.md.

Behavior changes to be aware of

• new UtilCollection(string) is stricter for every caller, not only through StringParser: empty or blank strings, stray braces, empty elements ({1,,2}, {1,}) and text after the closing brace now throw.
• Values are trimmed, and whitespace beside [ ] ; : = is removed. "{x1 : True}" now holds x1:True.
• Exception types change from System.Exception, InvalidOperationException and others to SpadeParseException. It derives from Exception, so existing catch (Exception) blocks still catch it.
• Grammar mistakes, such as a name that's never defined, still throw other exception types. That's tracked in fix(grammar): x is <set> and undefined names check nothing #14.

Testing

• dotnet test tests/SPADE.Tests: 96 passed (51 new). Commit 1 also passes on its own (81).

• Timing: 100,000 elements parse and print in well under a second (40,000 took 104 seconds before). 100 parses at the maximum depth also take well under a second. Depth 100,000 is rejected at position 257 instead of crashing.

• Fuzzing: 300,000 random strings and 300,000 random well-formed nested collections, run through StringParser with 8 grammars. Every failure was a SpadeParseException; no other exception type came out.

• Redux's full test suite (1,571 tests), with this whole stack plus the Redux changes from NODESET's grammar must use cross for its directed edges before the next SPADE upgrade Redux#629 and Move the ARCSET and SUBSETSUM malformed-certificate tests when Redux upgrades SPADE Redux#630: 1,567 passed, 0 failed, 4 skipped, the same as with the 0.1.2 package. Without #630's ARCSET test change, 2 fail: tests that expected malformed certificates to verify as False.

• Redux's whitespace tests (WhitespaceTolerance_Tests from Temporarily ignore whitespace in instances and certificates Redux#626) with Redux's own whitespace layer switched off:

  SPADE	Failed of 47
  0.1.2	45
  This branch	16

  All 16 remaining failures are in Redux code that doesn't read input through SPADE (hand-written verifiers and plain string comparisons), which Parse every certificate with SPADE, and make SPADE handle whitespace Redux#627 is moving onto SPADE.

Closes #2
Closes #4
Closes #7

[Trosper3]

Rebased the stack on #31 by merging (no force-push): this branch now has the rbs report, dotnet format (whitespace only; it's a separate style: commit), and tests on .NET 10 from #11. There are no code changes beyond that.