chore: drop unused root deps (pest/pest_derive/dirs), ignore tags+graph artifacts

improvise-v9w: the root `improvise` crate's [dependencies] listed pest,
pest_derive and dirs, none of which appear anywhere under src/. pest and
pest_derive remain genuine dependencies of improvise-formula and
improvise-io (persistence/improv.pest); examples/gen-grammar.rs reaches
pest_meta through [dev-dependencies], which examples do get, so the
examples still build. Verified with cargo build --workspace, cargo build
--examples, cargo test --workspace and the wasm check. Cargo.lock loses
only dirs and its transitive deps.

improvise-wg1: add the GNU Global tag files (GTAGS/GRTAGS/GPATH/GSYMS) and
the root graphviz artifacts (/graph.dot, /graph.html, /graph.svg) to
.gitignore. Named exactly rather than globbed so no checked-in asset is
swallowed; `git ls-files | git check-ignore --stdin` prints nothing.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EoW5BB87ZZdm96SvBTWawH

.gitignore

@@ -38,3 +38,14 @@ prolog-sessions/*
 *.gate.lock*
 .beads/embeddeddolt.incoming/
 .beads/embeddeddolt.previous/
+
+# GNU Global tag files (generated by the gtags devShell tooling)
+GTAGS
+GRTAGS
+GPATH
+GSYMS
+
+# graphviz/dependency-graph artifacts at the repo root
+/graph.dot
+/graph.html
+/graph.svg