fix(graph-ui): remove misleading 'Project name' field from index picker

[rarepops]

Split out from #739 at the maintainer's request, so this cross-platform change can be discussed as a standalone product / API-shape decision rather than riding along with the Windows navigation work.

What

Removes the optional Project name input from the index picker. Project names now always derive from the selected folder path.

Why

The field was labelled "Optional display name", but its value became the project's permanent identity, not a cosmetic label:

• the <name>.db filename,
• the projects.name primary key,
• the project. prefix on every node's qualified_name.

Since a project cannot be renamed after indexing and the name is always derivable from the folder path, the field was misleading.

Scope

• Removes the input, its React state, and its submit payload.
• Drops the now-dead projectName / projectNamePlaceholder i18n strings (EN + ZH).
• Updates the picker test accordingly.

The backend still accepts the project_name alias (#640), so this only removes the UI affordance; the request/response shape is unchanged. Happy to discuss whether the field should stay, be relabelled, or be removed as done here.

[rarepops]

Personally I would love this to stay and be properly implemented... I should be able to rename projects since I am not a fan of the default names they get now

[DeusData]

Heads-up: the security / codeql-gate failure on this PR is not your change — it was a repo-side gate bug (the check scanned only the 5 newest CodeQL runs and lost track of PRs on a busy queue). That's fixed on main now (#820). Any push to your branch — or simply clicking GitHub's Update branch button — will trigger a fresh run with the fixed gate and it should go green. Sorry for the noise, and thanks for your patience!

[DeusData]

Thank you for the clean split and the rigorous rationale — and for the patience while we weighed it. Decision: we're keeping the field but fixing the dishonesty you identified, rather than removing it. You're completely right that 'Optional display name' silently becoming permanent, un-renameable identity is a footgun; but removing the field costs the only human-friendly naming affordance in the UI, and the derived fallback names are the full flattened absolute path — rough in every dropdown and query scope. So the field stays with an honest label ('Project ID — permanent, cannot be renamed later') and matching help text, which lands shortly crediting you as co-author for driving the UX analysis. If a project-rename feature ships later, we'll revisit true cosmetic naming. Closing this PR per that decision — your #739 navigation work merges separately as soon as its rebase lands. Thanks again!