gh extension install --pin <tag> --force ignores pin when extension is already installed #13551

Summary

When an extension is already installed, running:

gh extension install OWNER/REPO --pin <tag> --force

appears to route through upgrade logic and installs latest, instead of honoring the pinned tag.

Environment

• OS: Linux
• gh version: 2.89.0 (2026-03-26)
• Example extension: github/gh-aw

Reproduction

1. Install an older version:
   gh extension install github/gh-aw --pin v0.74.8
2. Verify:
   gh extension list
3. Attempt forced pinned install:
   gh extension install github/gh-aw --pin v0.75.0 --force
4. Verify:
   gh extension list

Actual Behavior

The command upgrades to latest (for example v0.76.1) and prints upgrade-style output such as:

[aw]: upgraded from v0.74.8 to v0.76.1
✓ Successfully checked extension upgrades

Result: installed version is latest, not the pinned version.

Expected Behavior

When --pin is provided, it should be honored even if --force is also set and the extension is already installed.

Workaround

Removing first, then installing pinned works:

gh extension remove gh-aw
gh extension install github/gh-aw --pin v0.75.0

This correctly installs the pinned version.

Additional Context

This seems to happen because install with --force on an already-installed extension takes the upgrade path, and that path ignores pin for binary extensions (uses latest).