chore: replace skills/ with notte-skills submodule

[andreakiro]

Summary

• Removes the in-tree skills/notte-browser/ directory
• Adds nottelabs/notte-skills as a submodule at notte-skills/ (tracking main)
• Updates README link to the new path: notte-skills/plugins/notte-cli/skills/notte-browser/SKILL.md
• Removes .github/workflows/test-skills.yml (skill validation now lives in the notte-skills repo)

Test plan

• git submodule update --init --recursive populates notte-skills/
• Skill content reachable at notte-skills/plugins/notte-cli/skills/notte-browser/SKILL.md
• CI is green

[greptile-apps]

Greptile Summary

This PR migrates the in-tree skills/notte-browser/ documentation into a dedicated nottelabs/notte-skills git submodule, deletes the now-redundant test-skills.yml CI workflow, and updates the README link accordingly. No application logic is changed.

• Removes skills/notte-browser/ and the associated test-skills.yml workflow; skill validation responsibility moves to the notte-skills repo.
• Adds .gitmodules registering the submodule at notte-skills/ (tracking main) and pins the pointer to commit e718199.
• Updates the README Skills Documentation link to the new submodule path with a back-reference to the upstream repository.

Confidence Score: 5/5

Safe to merge — purely a documentation restructure with no code or logic changes.

The change removes static markdown/shell files from the tree, replaces them with a pinned submodule pointer, and updates one README link. There is no application code touched, no build system changes, and the existing Go CI workflows are unaffected.

No files require special attention.

Important Files Changed

Filename	Overview
.gitmodules	New file registering nottelabs/notte-skills as a git submodule at notte-skills/, tracking main branch.
README.md	Skills Documentation link updated to point to the new submodule path with a reference back to the upstream nottelabs/notte-skills repo.
.github/workflows/test-skills.yml	Workflow deleted; shell-script syntax checks and shellcheck lint for skills templates are now owned by the notte-skills repo.
notte-skills	New gitlink (submodule pointer) pinned to commit e718199.
skills/notte-browser/SKILL.md	Deleted from in-tree; content now lives in the notte-skills submodule.

_{Reviews (4): Last reviewed commit: "chore: replace skills/ with notte-skills..." | Re-trigger Greptile}