Validate safe-outputs target field at compile time

[Copilot]

Add compile-time validation for safe-outputs target field

Problem

The compiler previously accepted invalid values for the target field in safe-outputs configuration (e.g., target: event), which failed at runtime instead of during compilation.

Solution

Added compile-time validation in the compiler to catch invalid target values early:

Valid target values:

• "triggering" (default) - targets the triggering issue/PR/discussion
• "*" - targets any item specified in the output
• A positive integer like "123"
• A GitHub Actions expression like "${{ github.event.issue.number }}"

Invalid values rejected:

• Random strings (e.g., "event", "invalid")
• Zero ("0")
• Negative numbers ("-1")
• Numbers with leading zeros ("007")
• Malformed expressions

Implementation Details

• Created safe_outputs_target_validation.go with validation logic
• Added IsPositiveInteger utility function to pkg/stringutil package
• Added comprehensive unit tests in safe_outputs_target_validation_test.go and stringutil_test.go
• Added integration tests in safe_outputs_target_validation_integration_test.go
• Integrated validation into compiler flow in compiler.go
• Merged latest changes from main branch

Example Error Message

error: invalid target value for update-issue: "event"

Valid target values are:
  - "triggering" (default) - targets the triggering issue/PR/discussion
  - "*" - targets any item specified in the output
  - A positive integer (e.g., "123")
  - A GitHub Actions expression (e.g., "${{ github.event.issue.number }}")

Did you mean to use "${{ github.event.issue.number }}" instead of "event"?

This provides clear, actionable guidance to users when they make a mistake.

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[pelikhan]

@copilot use expression parser to validate correct expression, there should be a validator already

[pelikhan]

@copilot look for existing isPositiveInteger helper otherwise move to stringutils package, move tests too

[pelikhan]

https://gh.io/copilot-coding-agent-docs look for existing isPositiveInteger helper otherwise move to stringutils package, move tests too

[pelikhan]

@copilot look for existing isPositiveInteger helper otherwise move to stringutils package, move tests too

[Copilot]

@copilot look for existing isPositiveInteger helper otherwise move to stringutils package, move tests too

Moved IsPositiveInteger to pkg/stringutil package along with its tests (commit 80b3318). No existing helper was found in the codebase.

[pelikhan]

@copilot format the code, then merge main, then format and lint.

[Copilot]

@copilot look for existing isPositiveInteger helper otherwise move to stringutils package, move tests too

No existing helper found. Moved IsPositiveInteger and its tests to pkg/stringutil package (commit 80b3318). Completed code formatting, main branch merge, and final lint (commit 64f8453). All tests passing.