feat(extensions): configure an installed extension absent from source-sets

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Summary

v8-runner extensions --name <name> resolves configured extension source-sets.
It cannot configure an extension that was loaded separately as a CFE and is
known to the infobase only by its platform name.

Environment

• Windows
• 1C:Enterprise 8.3.27.1859, x86-64
• v8-runner 0.5.1

Reproduction

1. Load YAxUnit-25.12.cfe into a file infobase as extension YAXUNIT.
2. Keep the test extension source-set named TESTS in v8project.yaml.
3. Run v8-runner extensions --name TESTS.

The runner configures TESTS, but there is no supported invocation that also
updates the separately loaded YAXUNIT extension. YAXUNIT remains in safe
mode and cannot read its launch configuration file.

Expected behavior

The extensions operation should support selecting and configuring an
installed extension by platform name even when it is not represented by a
configured source-set.

Current workaround

Call the pinned platform tool directly:

ibcmd infobase --db-path <ib> config extension update
  --name YAXUNIT
  --safe-mode no
  --unsafe-action-protection no

The workaround must remain fail-closed until a released runner version supports
this operation.