#3013 auto-resolve: the Installing line prints the extension's entire multi-line description

Problem

When a command auto-resolves an extension from the registry, the Installing gutter line appends the extension's description in parentheses. The registry description is the extension's full README-style markdown (for @swamp/1password it is about 25 lines with headings, bullet lists and fenced code blocks), so a single status line becomes a wall of text that pushes the actual outcome off the screen.

Observed on swamp 20261003.133728.0-sha.bed0772a:

$ swamp vault migrate src --to-type @swamp/1password --yes
  Resolving   @swamp/1password not found locally, searching registry...
 Installing   @swamp/1password@2026.09.10.0 (Read, write, delete, and annotate secrets stored in 1Password using the `op` CLI.
Supports `swamp vault delete` for removing secrets and `swamp vault annotate`
... 20 more lines of README markdown ...
)
  Installed   @swamp/1password@2026.09.10.0 (1 models registered)

The rendering is renderAutoResolveInstalling in src/presentation/renderers/extension_auto_resolve.ts, which interpolates the description verbatim. The JSON event does not include the description, so only log mode is affected.

Proposed solution

Show only the first line (or first sentence) of the description, trimmed to a sane width, or drop the description from the Installing line altogether since the Installed line already names the extension and version.

Found while triaging swamp-club#3003.