solstone: reframe description to task-only, add Invoke + literal-command TRIGGER
Move the "Requires solstone to be installed with the sol CLI on PATH"
infrastructure detail out of the frontmatter description — the
Prerequisites section in the body already covers it. Keep the description
purely task-framed ("Query and search your solstone journal from any
project..."). Add sol call command literals to TRIGGER so sessions that
already know the commands still activate the skill. Add Invoke via Bash
line to the body summary.
This skill is installed user-wide via `npx skills add -g` by
`make install-service` (the dual-install pattern documented in the
synthesis plan) — intentional, not orphaned.
Part of skills audit req_loq3e2lk pass 1+2.