Add "around" constraint for fuzzy schedule syntax

[Copilot]

Implementation Complete: "around" Constraint in Fuzzy Scheduling

✅ All implementation tasks completed successfully!

• Add parser support for "daily around HH:MM" syntax
  • Extend parseBase() in schedule_parser.go to recognize "around" keyword
  • Create FUZZY:DAILY_AROUND:HH:MM format for around constraints
  • Reuse existing parseTime() parser for UTC and am/pm support
• Implement scattering algorithm for "around" constraint
  • Extend ScatterSchedule() to handle FUZZY:DAILY_AROUND pattern
  • Use deterministic hash-based scattering with bounded window around target time
  • Avoid quadratic algorithms (use simple hash modulo)
  • Window size set to ±1 hour (120 minutes total)
• Add tests for around constraint
  • Add parser tests for "daily around HH:MM" syntax
  • Add scattering tests for around constraint
  • Test edge cases (midnight, boundaries)
  • Add tests for UTC offsets with around constraint
  • Add tests for am/pm format with around constraint
  • Updated test assertions for ±1 hour window
  • Add comprehensive fuzz test coverage (20+ valid patterns, 12+ invalid patterns)
• Update documentation
  • Add "around" syntax to triggers.md
  • Add examples of around constraint usage
  • Document UTC and am/pm support
  • Updated all examples to reflect ±1 hour window
• Run validation and tests
  • Run parser unit tests (all pass ✅)
  • Run workflow tests (all pass ✅)
  • Run fuzz tests (134k+ executions, no crashes ✅)
  • Manually test compilation (works correctly ✅)
  • Format and lint code (all pass ✅)

Implementation Summary:

• Added support for daily around HH:MM syntax (e.g., daily around 14:00, daily around 9am)
• Reuses existing parseTime() function to automatically support:
  • UTC time offsets (e.g., utc+9, utc-5, utc+05:30)
  • am/pm format (e.g., 3pm, 11am)
  • Named times (midnight, noon)
  • 24-hour format (HH:MM)
• Scatters execution time within ±1 hour window of target time
• Uses O(1) hash-based algorithm (no quadratic complexity)
• Maintains deterministic behavior (same workflow → same scattered time)
• Handles edge cases like midnight and time boundaries correctly
• Comprehensive fuzz testing with 20+ valid and 12+ invalid seed patterns
• Documentation updated with examples and usage guidance

Example Usage:

on:
  schedule: daily around 14:00          # Scatters between 13:00-15:00
  schedule: daily around 3pm utc-5      # Scatters around 8 PM UTC (3 PM EST)
  schedule: daily around 9am utc+05:30  # Scatters around 3:30 AM UTC (9 AM IST)

The implementation is complete, tested, and ready for review.

Original prompt

Extend the fuzzy scheduling schedule syntax with "around" constraints

schedule: daily around <time>

which hints the scheduler to use a time close to the requested time.

This is not a hard constraint and the sub-optimal solution is allowed. Watch out for quadratic algorithms.

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[pelikhan]

@copilot support utc Time , am/pm. Reuse existing parser.

[pelikhan]

@copilot make +- 1 h

[Copilot]

@copilot support utc Time , am/pm. Reuse existing parser.

Done in commit 6180fe4. The implementation already supported UTC offsets and am/pm format by reusing the existing parseTime() function. Added explicit test coverage and documentation to make this clear.

Supported formats:

• daily around 3pm (am/pm)
• daily around 14:00 utc+9 (UTC offset)
• daily around 3pm utc-5 (both combined)
• daily around 9am utc+05:30 (UTC with HH:MM format)

[pelikhan]

@copilot update/add fuzz tests for the new format

[Copilot]

@copilot make +- 1 h

Done in commit 62269ee. Changed scattering window from ±2 hours to ±1 hour (120 minutes total window).

Example: daily around 14:00 now scatters between 13:00-15:00 instead of 12:00-16:00.

[Copilot]

@copilot update/add fuzz tests for the new format

Done in commit 16b132e. Added comprehensive fuzz test coverage including:

Valid patterns (20+ seeds):

• daily around 14:00, daily around midnight, daily around noon
• daily around 3pm, daily around 9am (am/pm format)
• daily around 14:00 utc+9, daily around 3pm utc-5 (UTC offsets)
• Various combinations of time formats and UTC offsets

Invalid patterns (12+ seeds):

• daily around (missing time)
• daily around 25:00, daily around 12:60 (invalid times)
• weekly around monday, monthly around 15 (wrong schedule type)
• hourly around 12:00 (unsupported)

Enhanced validation to properly handle FUZZY:DAILY_AROUND:HH:MM format. Fuzz test ran 134k+ executions without finding crashes or panics.