[IMPROVEMENT]: Derive snap version from git release tag at build time

[x15sr71]

In raising this pull request, I confirm the following (please check boxes):

Reason for this PR:

• This PR adds new functionality.
• This PR fixes a bug that I have personally experienced or that a real user has reported and for which a sample exists.
• This PR is porting code from C to Rust.

Sanity check:

• I have read and understood the contributors guide.
• I have checked that another pull request for this purpose does not exist.
• If the PR adds new functionality, I've added it to the changelog. If it's just a bug fix, I have NOT added it to the changelog.
• I am NOT adding new C code unless it's to fix an existing, reproducible bug.

Repro instructions:

This PR only changes the Snap CI workflow behavior; there is no runtime bug to reproduce in the binary.

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Description

This PR updates the Snap packaging workflow to derive the version at build time from the Git release tag, instead of relying solely on the hardcoded value in snap/snapcraft.yaml.

Background

The v0.96.6 GitHub release currently ships a Snap asset named ccextractor_0.96.5_amd64.snap, because snap/snapcraft.yaml still contains version: '0.96.5'.

That hardcoded value was originally chosen to avoid Snapcraft's 32-character version limit issues when using version: git (#1998) , and it is still useful as a safe default for local and manual builds.

For official releases, however, the Snap artifact version should match the release tag, in line with how the existing Windows release workflow derives artifact names from the tag.

There is one other place in CCExtractor's CI that already uses this "parse version from tag" pattern: the Windows release workflow (.github/workflows/release.yml, step "Get the version"). That step reads GITHUB_REF, strips the refs/tags/v prefix and any suffix after -, and uses the result when naming the Windows installer and portable artifacts.

Changes

Extend the existing "get version from tag" pattern from .github/workflows/release.yml to the Snap workflow (.github/workflows/build_snap.yml):

Add a Set Snap version from tag step that:

• Runs only on release events (if: github.event_name == 'release').
• Extracts the version from GITHUB_REF:
  • Strips the refs/tags/ prefix.
  • Strips an optional leading v (supports both v0.96.6 and 0.96.6 tags).
  • Drops any suffix after - (e.g. v0.96.6-rc1 → 0.96.6).
  • Removes whitespace and enforces a maximum length of 32 characters to respect Snapcraft version constraints.
• Verifies that snap/snapcraft.yaml contains a version: line before editing.
• Rewrites the version: line in snap/snapcraft.yaml to the parsed version in the CI workspace, immediately before running snapcraft --destructive-mode.

Behaviour

Repository state:

snap/snapcraft.yaml in Git remains unchanged with version: '0.96.5'. This continues to act as a default for local builds and any CI jobs that are not release builds.

Release builds:

For a tag such as v0.96.6, the workflow checkout starts with the hardcoded version: from snap/snapcraft.yaml (currently 0.96.5). The new step updates it in the CI workspace to version: '0.96.6', Snapcraft builds the Snap, and the resulting artifact is named ccextractor_0.96.6_amd64.snap. The modified file exists only in the CI workspace; no changes are committed back to the repository.

Manual / local builds:

Manual workflow_dispatch runs skip the version-rewrite step and continue to use version: '0.96.5'. Local snapcraft runs also use version: '0.96.5' from the file as before.

This keeps the hardcoded version as a safe fallback, but ensures that official release artifacts are aligned with the tagged version.

Testing

Local testing of the parsing and rewrite logic against snap/snapcraft.yaml:

Verified version extraction for different tag formats:

• GITHUB_REF=refs/tags/v0.96.6 → version: '0.96.6'
• GITHUB_REF=refs/tags/0.96.6 → version: '0.96.6'
• GITHUB_REF=refs/tags/v0.96.6-rc1 → version: '0.96.6'
• GITHUB_REF=refs/tags/v1.0 → version: '1.0'

Confirmed that:

• The script exits with an error if the parsed version is empty or longer than 32 characters.
• The script exits with an error if no version: line is present in snap/snapcraft.yaml.
• For valid tags, only the version: line is updated; the rest of snap/snapcraft.yaml remains unchanged.