aitools: expose supports_project_scope in aitools list --output json

[misha-db]

Changes

Adds a supports_project_scope boolean to every agent entry in the agents list
of databricks aitools list --output json.

• New SupportsProjectScope bool \json:"supports_project_scope"`field onagentEntryincmd/aitools/list.go, populated in buildAgentEntriesdirectly from the registry'sagents.Agent.SupportsProjectScope`.
• The field is always emitted (no omitempty), matching the existing managed
  and detected bools, so the JSON shape stays stable.

The value is true for the project-scope-capable agents (Claude Code, Pi,
Gemini CLI, Goose) and false for the rest.

Why

(can the CLI install a plugin) and detected (is the agent present), but nothing
told a consumer whether an agent is allowed to have project-scoped skills. That
capability lived only on the internal agents.Agent.SupportsProjectScope field.

The only project-scope signal in the JSON was a "project" key inside an agent's
installed map, which appears only when something is already installed there — so
consumers could infer capability positively but never learn it up front. Exposing
supports_project_scope lets the extension offer a project-scoped install without
hardcoding the agent list, mirroring how managed surfaces Plugin != nil.

Tests

Extended the existing unit tests in cmd/aitools/list_test.go:

• TestRenderListJSONWithAgents — asserts the JSON key round-trips (true for
  the claude-code fixture, false for the cursor entry), locking the contract.
• TestBuildAgentEntries — asserts the value is wired from the real registry:
  true for claude-code, false for codex (managed, global-only) and cursor
  (skills-only, global-only), so the test tracks reality if an agent's capability
  changes.