v0.3.0

Large trees used to take tens of seconds — or never finish. This release makes
them near-instant and reworks the interface around them.

Performance

• Dependency trees are linear, not exponential. A ROS dependency graph is a
  DAG: rcutils sits under nearly every branch. Expanding every path separately
  produced tens of thousands of duplicate nodes. Each package is now expanded once,
  where it first appears, and marked ↩ see above elsewhere — the same convention
  cargo tree uses. Measured on a 135-package install space plus a 24-package
  source workspace, resolving nav2_bringup with -r:

  depth	before	after
  5	4,152 nodes / 1.02 s	475 nodes / 0.02 s
  6	18,273 nodes / 4.44 s	548 nodes / 0.02 s
  7	68,081 nodes / 17.41 s	552 nodes / 0.02 s
  unlimited (the CLI default)	did not finish in 4 minutes	552 nodes / 0.02 s

  Pass --full to rostree tree for the old fully-expanded behaviour.

• Package discovery happens once. New rostree.core.index.PackageIndex scans
  every install prefix and source tree a single time and resolves names from memory.
  Previously every node of a tree could trigger a fresh recursive os.walk.

• package.xml parsing is memoized by path, mtime and size.

• Source scans prune build/, install/, log/, VCS metadata and directories
  marked COLCON_IGNORE/AMENT_IGNORE, and stop descending once a manifest is found.

• rostree graph resolves the whole DAG in one breadth-first pass instead of
  building a separate full tree per package.

Added

• rostree why <package> <dependency> — shortest dependency paths between two
  packages, answering "why is this in my tree at all?".
• rostree rdeps <package> — reverse dependency lookup, with --transitive
  and --workspace-only.
• rostree check — reports dependency cycles and unresolved dependencies and
  exits non-zero, so it can gate CI.
• rostree list --filter TEXT to narrow the package list.
• rostree tree --full, --expand-repeats, --max-nodes and -v for descriptions.
• --no-color on all commands (NO_COLOR is honoured too).
• NodeStatus enum on DependencyNode (ok, repeat, cycle, missing,
  parse_error, truncated) plus is_error/is_placeholder, replacing string
  markers stuffed into description. to_dict() now includes status.
• Public API: build_graph(), reverse_dependencies(), get_index(), tree_stats().
• TUI: live filter over every package, reverse-dependency view (v), dependency
  scope toggle (t), and a help screen (?).

Fixed

• Graphs no longer drop edges to unresolved packages. Dependencies without a
  manifest are drawn dashed and grey instead of being silently removed, which used
  to leave workspace graphs as a field of unconnected boxes. --hide-missing
  restores the old behaviour.
• rostree graph -w PATH now works on a workspace that is not sourced — the
  workspace's own packages are added to the search path.
• Unbuilt packages in a sourced workspace are found again. The source root was
  derived as <ws>/install/src instead of <ws>/src, so src-only packages were
  invisible whenever the workspace was discovered through AMENT_PREFIX_PATH or
  COLCON_PREFIX_PATH. Both the merged (<ws>/install) and isolated
  (<ws>/install/<pkg>) colcon layouts are now handled.
• Packages named lib* are no longer discarded. libstatistics_collector and
  libyaml_vendor are real ROS 2 packages; only dashed rosdep keys
  (libboost-dev, python3-numpy) are treated as system dependencies, and those
  are now kept on PackageInfo.system_dependencies rather than dropped.
• The TUI no longer freezes while a tree is built: resolution runs on a worker
  thread and rows are created only as nodes are expanded.
• The TUI package list is no longer capped at 80 entries per source.
• Text trees use correct box-drawing characters (└── for last children, proper
  vertical guides); previously every child was drawn as ├──.
• An unknown package name is now an error with suggestions and a non-zero exit,
  instead of a one-node tree and exit 0.
• The five duplicated hand-rolled <name> XML scrapers were replaced by a single
  quick_package_name() helper.
• Worker results in the TUI are routed to the callback that asked for them, rather
  than to whichever handler saw the completion event first.
• ↩ see above now always refers to something printed earlier. Expansion was
  chosen by shortest distance from the root while the tree renders depth-first, so
  a back-reference could point at a subtree printed below it. Each package is now
  expanded where the tree first prints it, which also removes a whole breadth-first
  pass from tree building.
• Reverse dependencies were cached without keying on the dependency tag set, so a
  runtime-only lookup and a full lookup returned whichever ran first.
• rostree why <pkg> <pkg> reported a dependency path for a package that does not
  exist; the validation loop skipped both arguments when they were equal.
• Global flags such as --no-color are accepted after the subcommand too
  (rostree tree rclcpp --no-color used to be a usage error).
• TUI: pressing e (expand all) or running a search no longer duplicates every
  row of an already-expanded tree.
• TUI: selecting a second package while a tree is still building no longer leaves
  the app pointing at a tree it never rendered.
• TUI: adding a source path while a tree is open now rescans, instead of leaving
  the new packages invisible.
• TUI: Esc leaves the dependents view when it was opened from the package list.
• --open no longer goes through a shell on Windows: it uses os.startfile, so a
  path containing shell metacharacters cannot be misinterpreted. External tools
  (dot, open, xdg-open) are resolved to absolute paths before being executed.

Changed

• rostree tree groups sibling back-references onto one line
  (↩ 5 already shown above: …); --expand-repeats lists them individually.
• Depth-limited nodes report how many dependencies are hidden (… 5 more).
• rich is now a direct dependency (it was already installed via textual).
• Lint rules are pinned in pyproject.toml so a new ruff release cannot change
  what CI enforces.