fix(system): add openSUSE platform support

[peplocanto]

🔗 Linked Issue

Closes #140

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🏷️ PR Type

What kind of change does this PR introduce?

• type:bug — Bug fix (non-breaking change that fixes an issue)
• type:feature — New feature (non-breaking change that adds functionality)
• type:docs — Documentation only
• type:refactor — Code refactoring (no functional changes)
• type:chore — Build, CI, or tooling changes
• type:breaking-change — Breaking change (fix or feature that changes existing behavior)

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📝 Summary

Adds openSUSE family support so gentle-ai no longer exits with unsupported linux distro on openSUSE Tumbleweed/Leap systems detected through /etc/os-release.

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📂 Changes

File / Area	What Changed
internal/system	Detects openSUSE-family distros and maps them to zypper with supported platform status
internal/installcmd	Resolves zypper dependency installs and enables openSUSE paths for OpenCode, GGA, and Kimi uv hints
internal/cli	Clarifies optional Go messaging and Engram PATH guidance now that non-brew Engram uses released binaries
e2e/	Adds an openSUSE Tumbleweed Docker E2E target and includes it in the platform matrix
docs/ and PRD.md	Documents openSUSE support, zypper commands, and optional Go behavior

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🧪 Test Plan

Unit Tests

go test ./...

E2E Tests (Docker required)

sg docker -c './e2e/docker-test.sh'

Additional local verification:

git diff --check
go build -o /tmp/gentle-ai-opensuse ./cmd/gentle-ai
gentle-ai install --dry-run
timeout 5s script -q -c "gentle-ai" /dev/null

Results:

• Unit tests pass (go test ./...)
• E2E tests pass (sg docker -c './e2e/docker-test.sh', PASSED: 4 / 4)
• Manually tested locally on openSUSE Tumbleweed
• gentle-ai install --dry-run reports os=linux distro=opensuse package-manager=zypper status=supported
• Installed patched binary starts the TUI under a pseudo-terminal without the unsupported distro error

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🤖 Automated Checks

The following checks run automatically on this PR:

Check	Status	Description
Check Issue Reference	⏳	PR body must contain Closes/Fixes/Resolves #N
Check Issue Has status:approved	⏳	Linked issue must have been approved before work began
Check PR Has type:* Label	⏳	Exactly one type:* label must be applied
Unit Tests	⏳	go test ./... must pass
E2E Tests	⏳	cd e2e && ./docker-test.sh must pass

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✅ Contributor Checklist

• PR is linked to an issue with status:approved
• I have added the appropriate type:* label to this PR
• Unit tests pass (go test ./...)
• E2E tests pass (cd e2e && ./docker-test.sh)
• I have updated documentation if necessary
• My commits follow Conventional Commits format
• My commits do not include Co-Authored-By trailers

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💬 Notes for Reviewers

The openSUSE E2E target uses opensuse/tumbleweed:latest and validates the same Tier 1 dry-run smoke suite as the existing Linux Docker matrix.

[Alan-TheGentleman]

The openSUSE support looks potentially valuable, but the process gates are missing.

Please add the required type:* label, confirm the linked approved issue, and refresh CI after rebasing on main so we review current code instead of a stale branch.

[Alan-TheGentleman]

Heads-up: this PR is now showing a merge conflict against main. We shipped v1.31.0 (and a number of follow-up fixes) over the past two days — several files this PR touches were also modified upstream.

Could you rebase against current main and resolve the conflicts?

git fetch upstream main
git rebase upstream/main
# resolve any conflicts
git push --force-with-lease

Once it's green again I can review for merge. Sorry for the drift — it's the cost of the cleanup velocity. Thanks for sticking with it.