refactor: make shareable components abstract

[bepri]

This PR prepares for the creation of other Node-based Craft Actions by refactoring the pieces of Rockcraft's pack action that seemed shareable out into "common" modules. I tried my best to keep the task focused and break up the commits, but frankly this was just a very loud PR. Sorry.

I made a temporary repository with two CI runs to validate this: https://github.com/bepri/test-actions/actions

The first run was the simplest case, just rockcraft init with a standard, optionless call to this action. The second run used an unmaintained base and customized many of the options.

[Copilot]

Pull request overview

This PR refactors the Rockcraft pack action to extract reusable, tool-agnostic building blocks (a shared CraftBuilder base class and a shared runPackAction/input reader), in preparation for additional Node-based Craft Actions.

Changes:

• Introduced an abstract CraftBuilder (common pack/test execution, artifact discovery, pro/verbosity handling) and updated RockcraftBuilder to extend it.
• Added a shared pack-action helper (readBaseInputs, runPackAction) and migrated rockcraft-pack-action to use it.
• Generalized tool capability checks (haveFlag, haveSubcommand) and updated/added unit tests accordingly; simplified bundling via scripts/pack.mjs.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/tools.test.ts	Updates tests to cover ensureCraftTool, haveFlag, and haveSubcommand.
tests/rockcraft-pack.test.ts	Refactors tests to align with the new CraftBuilder-based implementation and focuses on Rockcraft-specific behavior (--ignore).
tests/pack-action.test.ts	Adds unit tests for the new shared readBaseInputs and runPackAction.
tests/craft-builder.test.ts	Adds comprehensive tests for the new CraftBuilder behavior (pack/test flow, flags, artifact discovery).
src/tools.ts	Generalizes Rockcraft-specific helpers into haveFlag, haveSubcommand, and ensureCraftTool.
src/rockcraft-pack.ts	Converts RockcraftBuilder into a CraftBuilder subclass and moves shared logic to the base class.
src/rockcraft-pack-action.ts	Switches the action entrypoint to the new shared pack-action helpers (but currently instantiates the builder at module scope).
src/pack-action.ts	Adds shared input parsing and standardized pack+artifact output logic.
src/craft-builder.ts	Introduces the abstract shared builder implementation used by tool-specific builders.
scripts/pack.mjs	Adds a dedicated esbuild bundling script.
package.json	Updates pack script to use scripts/pack.mjs.
dist/rockcraft-pack-action/index.js	Updates the bundled output to reflect the refactor.

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[smethnani]

This looks great!

[alesancor1]

Many comments, but honestly the refactor is really good.

My comments are mostly regarding the repository structure and file names. The logic itself looks good to me, fantastic work!

Afaict none of the suggestions below would alter the current behaviour of the action, since it's just moving stuff around and removing some unnecessary checks:

[alesancor1]

LGTM!

Looking forward to see more actions coming in once the new structure is in place!