Cycle through ambiguous matches with Tab in the Add project path input

[simonjohansson]

Problem

In the Add project path browser (Cmd+Shift+O), Tab completes a path when exactly one entry
matches, and extends to the common prefix when several do. Once the prefix can't grow, Tab does
nothing, so picking among similarly named folders means reaching for the arrow keys or typing
until the match is unique.

Example, with Model, ModelDigi, and ModelDigi-85 in ~/src:

• ~/src/Mod + Tab → ~/src/Model (works today)
• Tab again → nothing

Proposal

Shell-style menu completion, like zsh:

• First Tab still extends to the common prefix (unchanged).
• When the prefix can't extend further, Tab cycles through the matches, replacing the input:
  ~/src/Model/ → ~/src/ModelDigi/ → ~/src/ModelDigi-85/ → ~/src/Model/
• Shift+Tab cycles backwards.
• While cycling, the list keeps showing the matching siblings with the current one highlighted,
  instead of flipping to each folder's contents.
• Typing ends the cycle and continues inside the selected folder (~/src/ModelDigi/ + s →
  ~/src/ModelDigi/s). Enter adds the selected folder as today.

Scope

• Web and desktop only. Mobile has no Tab key.
• The clone destination step is unchanged (it already skips prefix completion).
• No server, contract, or settings changes. The cycling logic sits next to the existing
  getFilesystemBrowseTabCompletion helper in packages/client-runtime, plus the Tab handler
  in CommandPalette.tsx.

Related: #1599 (original directory autocomplete request).

I'm happy to implement this if the direction and scope look right.