Fix date math rounding to respect inclusive/exclusive bracket boundaries

[niemyjski]

Summary

• Fix bracket-aware rounding in TwoPartFormatParser: Previously, rounding (/d, /M, /h, etc.) always rounded down for the start side and up for the end side regardless of bracket type. Now follows Elasticsearch conventions where inclusive brackets ([, ]) maximize the matched range and exclusive brackets ({, }) minimize it.
• Support mixed bracket pairs: [start TO end} and {start TO end] are now valid, matching Elasticsearch Lucene query syntax. Previously these were rejected as mismatched.
• Performance: Replaced regex pre-scan with a simple backwards character scan to detect the closing bracket. Wildcard parsers still receive positional isUpperLimit since they use it for min/max semantics, not rounding.
• Documentation: Added a "Rounding with Inclusive/Exclusive Ranges" section to README with a reference table and common date range patterns.

Rounding Rules

Boundary	Bracket	Rounding	Elasticsearch equivalent
Min (start)	[ inclusive	Round down (start of period)	gte
Min (start)	{ exclusive	Round up (end of period)	gt
Max (end)	] inclusive	Round up (end of period)	lte
Max (end)	} exclusive	Round down (start of period)	lt

Examples

• [now/d TO now/d] — entire current day (start-of-day to end-of-day)
• [now/d TO now/d} — start-of-day to start-of-day (empty/collapsed)
• {now/d TO now/d] — end-of-day to end-of-day (empty/collapsed)
• [now-1d/d TO now/d} — start of yesterday to start of today (lt semantics on end)

Ref: FoundatioFx/Foundatio.Lucene@a8426ab

Test plan

• All 684 existing tests pass (no regressions)
• New TwoPartFormatParserTests: exclusive brackets ({jan TO feb}, {2012 TO 2013}), mixed brackets ([2012 TO 2013}, {2012 TO 2013]), wildcard with exclusive brackets ({2012 TO *})
• New DateTimeRangeTests: all four bracket combos with /d rounding, /M rounding, /h rounding, mixed brackets with date math operations
• Build succeeds with 0 warnings, 0 errors
• dotnet format passes with no changes needed

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[Copilot]

Pull request overview

Adjusts date range parsing to make date-math rounding bracket-aware (inclusive/exclusive) and align behavior with Elasticsearch range-query conventions, while also allowing mixed bracket pairs.

Changes:

• Updates TwoPartFormatParser to determine rounding direction based on inclusive ([ ]) vs exclusive ({ }) boundaries, and allows mixed bracket pairs.
• Adds/updates tests covering exclusive + mixed bracket combinations and /d, /M, /h rounding behaviors.
• Expands README documentation with a bracket-aware rounding reference section and common patterns.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
tests/Exceptionless.DateTimeExtensions.Tests/FormatParsers/TwoPartFormatParserTests.cs	Adds coverage for exclusive and mixed bracket pairs (and updates wildcard expectations).
tests/Exceptionless.DateTimeExtensions.Tests/DateTimeRangeTests.cs	Adds end-to-end parsing tests for bracket-aware rounding across units and mixed brackets.
src/Exceptionless.DateTimeExtensions/FormatParsers/FormatParsers/TwoPartFormatParser.cs	Implements bracket-aware rounding direction + mixed bracket acceptance; changes closing-bracket detection.
README.md	Documents inclusive/exclusive rounding rules and provides example patterns.

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