feat(spec): add Kiro / Amazon Q CLI autocomplete spec

[bthnkucuk]

Summary

Adds a Fig.Spec autocomplete spec for fastlane_cli consumed by Amazon Q
Developer CLI for command line (formerly Fig) and Kiro CLI. Surfaces
inline AI ghost-text + rich dropdown completions for every subcommand,
option, and argument exposed by lib/src/cli/.

• New: dist/amazon-q-spec/fastlane_cli.ts — the spec itself.
• New: dist/amazon-q-spec/README.md — how to test locally, how to
  typecheck standalone, where the upstream copy lives.
• One-line mention in the root README.md pointing users at the spec dir.
• Version bump to 0.2.0 in pubspec.yaml + dist/homebrew/Formula/fastlane_cli.rb
  per the fastlane-cli-version-bump skill
  (new shipped surface => minor).

Why a copy lives here

The spec is mirrored upstream at withfig/autocomplete/src/fastlane_cli.ts
(the spec collection consumed by Q + Kiro). Tracking it in our own repo
means:

1. It travels with the CLI version it describes.
2. Drift between code and spec gets caught by the same reviewers who own
   lib/src/cli/*_command.dart.
3. Users can opt into the spec before the upstream PR lands by pointing
   their local dev-mode autocomplete clone at this file.

Generator pattern (no static action lists)

The run <action-id> arg and list --category <id> arg both use a
generator that runs fastlane_cli list --json and parses the result. The
JSON shape (id, title, description, category) is emitted by
list_command.dart. Cached for 5s inside the autocomplete runtime.

This means the spec never goes stale when consumers add custom
actions in their cli_profile.yaml — the dropdown reflects whatever
fastlane_cli list --json reports.

Opt-in (local dev-mode)

Until the upstream PR is merged, users can preview the spec locally:

git clone https://github.com/<you>/autocomplete.git
cd autocomplete && pnpm install
cp <fastlane_cli>/dist/amazon-q-spec/fastlane_cli.ts src/
pnpm dev
# In another terminal: type `fastlane_cli ` and hit space.

Upstream PR

Sibling PR against withfig/autocomplete:
withfig/autocomplete#2625

Test plan

• fvm dart analyze — No issues found!
• fvm dart test — 193/193 passing
• TypeScript typecheck (TS ~5.5.4 + @withfig/autocomplete-types@^1.31.0):
  passes against the entire upstream src/ tree.
• prettier --check against the upstream config: passing.
• Every flag in the spec maps 1:1 to an option declared in the
  matching lib/src/cli/*_command.dart.
• fastlane_cli list --json shape confirmed in code: id,
  title, description, category.