fix(macos): title-case profile name when label is missing or blank

[ashleeradka]

Closes LUM-1519.

Prompt / plan

InferenceProfile.displayName is read by the chat composer pill, the
profile list, the default-profile dropdown, the composer settings menu,
and a handful of accessibility labels. It fell back to the raw name
identifier whenever label was nil. On Cloud, the platform-overlay
seeds profiles without populating label (assistant/src/config/seed-inference-profiles.ts
short-circuits re-seeding under isPlatform once a profile entry
exists), so freshly hatched assistants showed kebab-case identifiers
like quality-optimized — or nothing at all if the label happened to
be an empty string rather than nil — in spots that should read
"Quality Optimized".

Make the fallback empty-aware (treat "" and whitespace as missing,
not just nil) and title-case the name when it fires. The name
field itself stays untouched; it's the stable identifier used as the
profile key in lookups, the conversation override, and call-site
overrides.

Noa is separately addressing the underlying data issue (why label is
blank for new assistants on Cloud); this PR is the UI-side hardening
explicitly requested in the ticket.

What changed

• clients/macos/vellum-assistant/Features/Settings/InferenceProfile.swift
  • displayName now returns label only when it is non-nil and
    non-empty after trimming; otherwise it returns
    Self.titleCased(name).
  • Adds static func titleCased(_:) which splits on -, _, and
    whitespace, capitalises the first character of each non-empty part,
    and joins with single spaces. Falls through to the input unchanged
    when no usable parts remain (e.g. "---").

Why this is safe

• Pure UI display change. No wire format, persistence, IPC, or
  NotificationCenter payload touches the change.
• No cross-component skew: the daemon, gateway, and platform never see
  the rendered string. Old daemon + new macOS and new daemon + old
  macOS both behave identically since this lives entirely inside the
  macOS client's render path.
• All existing call sites of displayName (profile list rows,
  ChatProfilePicker.label, InferenceServiceCard dropdown options,
  ComposerSettingsMenu profile picker, accessibility labels in
  InferenceProfilesSheet) benefit transparently — no call-site
  changes needed.

Alternatives considered

• Mutate name at decode time so it's pre-formatted. Rejected:
  name is the stable identifier used as a profile key in
  activeProfile lookups, id, call-site overrides, and conversation
  override fields. Display formatting must remain a derived view-only
  concern.
• Add a fallback at each call site. Rejected: at least five call
  sites depend on displayName. Centralising in the computed property
  keeps the convention enforceable and the test surface narrow.
• Use String.capitalized directly. Rejected:
  "quality-optimized".capitalized returns "Quality-Optimized"
  because Foundation's capitalized
  treats - and _ as part of a word, not a separator.
• Backend backfill mirroring #30412
  (provider connections). Out of scope per the ticket — Noa is
  handling the root-cause data issue separately. UI hardening also
  guards against future label-blank scenarios.
• Extract a shared String extension and DRY up with
  MessageInspectorSummaryFormatters.titleCasedProviderLabel.
  Considered but explicitly de-scoped for this PR per request: the
  ticket asks for the minimal UI fallback while the data root cause is
  being fixed separately. The provider-label helper lives in a
  different domain (inspector summary) and a follow-up consolidation
  is safer once both call sites have settled.

Test plan

• Updates the existing InferenceProfile displayName tests in
  InferenceProfileTests.swift to expect the title-cased fallback:
  • nil label → title-cased name
  • empty-string label → title-cased name
  • whitespace-only label → title-cased name
• Adds testTitleCasedHandlesCommonIdentifierShapes covering
  balanced, quality-optimized, custom_balanced,
  custom-quality-optimized, surrounding/repeated whitespace, all
  separators (---), and empty input.
• Updates the affected ChatProfilePickerTests cases that previously
  encoded the raw-kebab fallback ("Default (balanced)",
  "quality-optimized", "Default (cost-optimized)") to the
  title-cased output.
• CI doesn't build macOS — Xcode build/test must be verified locally
  before merging.

Root cause analysis

1. How did the code get into this state? displayName was added
   as label ?? name when the label/source/description fields
   landed. At the time, every seeded profile included a label, so
   the fallback was only ever exercised by ad-hoc user-created
   profiles where the kebab name was acceptable.
2. What mistakes or decisions led to it? The fallback path was
   never explicitly designed for the platform-overlay case where
   label is missing. The decoder normalises "" to nil, which
   masked the empty-string scenario in unit tests and meant the gap
   only surfaced once the Cloud platform started serving
   label-less profiles.
3. Were there warning signs we missed? #30412
   fixed the same symptom for provider connections (label blank,
   editor renders empty) by backfilling label = name. The same
   pattern across the codebase suggests a generalised "always have a
   sensible display fallback when label is missing" convention is
   missing.
4. What can we do to prevent this pattern from recurring? Any
   identifier field paired with a user-friendly label should
   compute a display value that is presentable even when label is
   absent. Title-casing the identifier is the cheap, reliable
   default.
5. Should we add a guideline to AGENTS.md? Not yet. Two data
   points (InferenceProfile, provider connections) is suggestive
   but not enough to warrant a project-wide rule; a follow-up that
   factors out a shared titleCasedIdentifier extension would be the
   right time to codify the convention.

References

• Apple — String.capitalized
  (why we can't use it directly: keeps - and _ as part of a word)
• Apple — CharacterSet
• Apple refs checked (2026-05-12): String.capitalized, CharacterSet.union(_:), String.components(separatedBy:)

Link to Devin session: https://app.devin.ai/sessions/bac5a01cf5be4de69e79e16034b50cfb
Requested by: @ashleeradka

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LUM-1519

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