fix(variables): add noop mode support

[klutchell]

Fixes: #925

• Add noop mode support to Variables plugin add/remove/update methods
• Return NopCommand instead of making API calls when nop=true
• Add comprehensive tests for noop mode behavior

Refactor Variables plugin to match the single-item Diffable contract
used by labels, milestones, and other plugins. The previous update()
reimplemented sync() logic internally; now each method handles one item
and lets Diffable.sync() orchestrate iteration.

• Simplify update() from 90-line array-diffing to single-item PATCH
• Simplify changed() from JSON.stringify comparison to value check
• Remove getChanged(), lodash dependency, .then(res=>res) no-ops
• Match labels.js nop return pattern: Promise.resolve([NopCommand])
• Fix inconsistent toUpperCase() between add/remove/update
• Let errors propagate to Diffable.sync() instead of swallowing
• Normalize find() to strip API metadata fields (created_at, etc.)

[Copilot]

Pull request overview

Adds proper noop (dry-run) behavior to the variables plugin so repository variables are not mutated when nop: true, addressing safe-settings issue #925.

Changes:

• Added NopCommand-based noop handling to Variables.add(), Variables.remove(), and Variables.update() to avoid mutating API calls in dry-run mode.
• Expanded unit tests to cover noop behavior for add/remove/update and adjusted test setup to pass nop into the plugin.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
lib/plugins/variables.js	Adds noop checks and returns NopCommand(s) instead of performing POST/PATCH/DELETE when nop is enabled.
test/unit/lib/plugins/variables.test.js	Adds unit tests validating noop behavior for variables operations and updates test harness to pass nop.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

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[klutchell]

@decyjphr this one should be good to go!

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

lib/plugins/variables.js:178

• In noop mode, update() currently returns nopCommands.length === 1 ? nopCommands[0] : nopCommands, which means it can return [] when changed is true but no concrete operations are generated. That bubbles up through Diffable.sync() and can produce non-NopCommand items in the returned results array. Consider returning undefined/null when nopCommands.length === 0 (or ensuring changed is only true when an operation will be emitted).

      if (this.nop) {
        return nopCommands.length === 1 ? nopCommands[0] : nopCommands
      }

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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[klutchell]

@decyjphr conflicts resolved