Picker abstraction and external fuzzy finders

[raiseCatError]

Goal

A picker abstraction so NMSh selection surfaces can use the Native picker (default) or an optional external fuzzy finder.

Provider	Role
NMSh Native	Default
fzf	Optional external
Television	Optional external

Potential uses

files · directories · history · sessions · Git branches · processes · tool selection

Architectural constraints

• NMSh supplies the candidate list (for example on stdin) and receives the selection. The selection is inserted into the editor or used for an explicit NMSh action, never executed automatically.
• External pickers run through a controlled terminal handoff similar to passthrough: terminal modes are restored on accept, cancel, resize and error.
• Missing or failing external pickers fall back to Native (Provider framework and unified provider UX #134).

Non-goals

• Configured-zsh completion parity and fzf-tab interoperability #52 stays parked. Picker providers are not a route to fzf-tab or configured-zsh completion parity.
• Replacing NMSh-owned panels that are not pickers (settings, prompt editor).

Acceptance criteria

• A picker interface is used by at least one NMSh surface, for example history or directories.
• fzf and Television work as providers with clean terminal restoration.
• Selections never auto-execute.

Dependencies / related

Part of #134. Related #143, #146, #147, #130.

Research references

• fzf: https://github.com/junegunn/fzf
• Television: https://github.com/alexpasmantier/television

[raiseCatError]

Development implementation is reviewable in #237; final acceptance documentation is #241. These are dependent, unmerged PRs on current dev, with no release/version bump.

The complete code head passed 714 local tests, build, typecheck, benchmark types and diff checks, plus Node 22/26 CI. Architecture and limitations describe what is implemented and deferred. One physical-QA checklist covers the relevant keyboard/layout/provider/privacy checks; it has not been performed.

This issue stays open until release. Project status could not be updated because the available token lacks read:project; active branches/PRs provide durable work status.

[raiseCatError]

Implemented on the v0.16 branch (PR #303, feature/v016-platform-portability-agents). Picker abstraction with Native, fzf and Television providers and fallback to Native; selections never execute: src/pickers/, tests/picker.test.ts. It was part of the integrated build the maintainer physically validated in the earlier v0.16 QA pass; closing with the implementation.