pgrls-vscode v0.2.1

Follow-up safety/correctness release on top of v0.2.0.

Changed

• Apply-fixes safety. "Apply fixes to database…" now always runs
  the dry-run first, prints the exact SQL to the pgrls output channel,
  and the confirmation states plainly that the target DB is whatever
  pgrls resolves from pgrls.databaseUrl → $DATABASE_URL →
  pgrls.toml (not necessarily a local dev database) — so a
  $DATABASE_URL pointed elsewhere can't be mutated from a
  dev-looking prompt. The confirmation also notes that pgrls re-checks
  the live schema at apply time, so the applied statements may differ
  from the previewed SQL if the database changed in between.
• No-op fixes show a notification, not an empty editor. When
  pgrls fix finds nothing to remediate, both Quick-Fix actions now
  show a "nothing to fix" notification instead of opening an editor
  with a placeholder comment.

Fixed

• Explain a rule… now opens the right page for DIFF_* rules.
  The command accepts diff-rule IDs (e.g. DIFF_DROP_POLICY) but was
  sending them to a dead docs/RULES.md anchor; diff rules are
  documented in AGENTS.md. The rule-ID → docs-URL mapping is now
  shared (ruleDocs.ts) across the command, the hover, and the
  diagnostic link so all three route identically. The command's input
  box also validates against the real rule families
  (SEC/PERF/HYG/VIEW + DIFF_*), rejecting malformed IDs.
• README now documents the full hover fallback (also fires for
  DIFF_* rule IDs, which aren't in the lint catalog the hover
  caches).
• Removed stale "v0.1.0 scaffold" comments (one misdescribed the
  shipped Explain a rule… command).
• pgrls.lintOnSave setting description now lists all three triggers
  (.sql, .plpgsql, pgrls.toml) and fixes a .pgrls.toml typo.