fix(install): Name the bundle in the install summary

[ananos]

Summary

The installer's summary ended with

[brig-install] brig v0.1.0-rc8 is installed (user)

where v0.1.0-rc8 is the bundle's release, not brig's. Installed through brig's
own install.sh, the next line then read

brig-install: installed brig v0.2.0 into the runtime at /home/<user>/.local/share/brig/data/bin

so one install reported two brig versions. This came up in a rootless user
install on Ubuntu 24.04, next to a brig-side fix for the same run's PATH advice
(brig-sh/brig#352).

Changes

• The line now reads the brig runtime bundle v0.1.0-rc8 is installed (user).
  brig's version stays in pins.env, which brig-ctl version prints.
• tests/install-summary.sh, run by the Script tests CI step (the same step as
  fix(rootless): Give each user a device grant of their own #6 and fix(bundle): Run brig-ctl's ctr inside the rootless namespace #8, word for word).

Testing

tests/install-summary.sh runs install.sh as a user install on a minimal fake
bundle (BUNDLE_VERSION=v9.9.9, a brig and a stub setup), with stubs for the
host checks:

$ sh tests/install-summary.sh
ok - the summary names the bundle and its version

The same test against the previous install.sh:

$ sh tests/install-summary.sh
[brig-install] brig v9.9.9 is installed (user)
...
FAIL: the summary does not name the bundle

sh -n (dash) and shellcheck -s sh pass over install.sh,
build-bundle.sh, the three generated scripts and the test. All four open
bundle branches (#6, #7, #8 and this one) apply to main together without a
conflict, and the four tests pass on the result.

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