build: add project C++ warning set and configure ruff lint rules

[maxwbuckley]

Description

Two related build-hygiene changes that were previously unenforced.

1. build: project C++ warning set with opt-in warnings-as-errors

Adds cmake/CompilerWarnings.cmake, included from the root CMakeLists.txt after
add_subdirectory(deps). Directory-scope compile options are only inherited by
subdirectories added after the call, so first-party targets get the flags while the
third-party trees (OpenXR SDK, yaml-cpp, pybind11, mcap, flatbuffers, Catch2) keep
their own.

Flags on GNU/Clang: -Wall -Wextra -Wno-missing-field-initializers -Wnon-virtual-dtor -Woverloaded-virtual -Wimplicit-fallthrough -Wextra-semi. MSVC gets /W4 /permissive-.
Two options: ISAAC_TELEOP_ENABLE_WARNINGS (ON) and ISAAC_TELEOP_WARNINGS_AS_ERRORS
(OFF, opt in per build/CI).

Fixes everything the set surfaced:

• properties.serial is a fixed char[256], never a pointer, so the
  properties.serial ? ... : "" guard was always-true dead code
  (-Wpointer-bool-conversion, 3 sites). Replaced with a strnlen-bounded
  std::string construction, which additionally guards against a runtime that fills
  the array without a terminator.
• Removed the empty, unused print_xdev_info (-Wunused-function).
• Commented out the unused argc parameter name in six main() definitions.

robstride_bus's private members are used only inside #ifdef __linux__, so Clang
reports them unused when the file compiles to its throwing stub. That warning is
correct but unactionable off Linux (GCC has no equivalent), so it is suppressed for
that one target on non-Linux only.

2. chore: ruff lint rules, and the fixes they surfaced

The ruff and ruff-format pre-commit hooks were running with no configuration at
all, so only ruff's built-in defaults (E4/E7/E9 + F) were ever enforced. Adds a
[tool.ruff] section selecting the correctness-oriented groups: B, C4, PIE, PERF,
PLE, PLW, LOG, G, ASYNC and RUF. Formatting is unchanged (ruff-format defaults, which
the tree already matches). Everything in select is currently clean, so the hook is
enforceable as-is. Each entry in ignore is a deliberate call with its reason inline.

Bug-shaped findings fixed:

• B023: a closure captured the loop variable phase in the synthetic camera source.
  Hoisting it above the loop and passing phase explicitly also stops rebuilding the
  closure on every generated frame.
• RUF043: pytest match="libcloudxr.so" treated . as a regex wildcard where a
  literal filename was meant; the remaining patterns are intentional regexes and are
  now raw strings.
• RUF012: three mutable class attributes annotated ClassVar, one of them on the
  EnvConfig singleton.
• LOG014: pass the caught exception via exc_info=exc rather than relying on ambient
  sys.exc_info().
• RUF013 implicit Optional, B904 exception chaining, B011 assert False (removed
  by python -O), B017 blind pytest.raises(Exception), G004 eager f-string log
  formatting, PLW1510 implicit subprocess check, plus safe C4/PIE/PERF/RUF autofixes.

TRY004 (ValueError -> TypeError in TeleopSessionConfig validation) was left
alone: it is a public API behaviour change, not a lint fix.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Testing

Validated on two toolchains.

Apple Clang 21 / arm64 (macOS) — 88 first-party TUs configure on that host. Clean
build with ISAAC_TELEOP_WARNINGS_AS_ERRORS=ON. ctest 158/160, the two failures being
environment gaps (no wuji-sdk wheel, no CloudXR SDK tarball) confirmed pre-existing by
re-running with these changes stashed.

GCC 13.3 / x86_64, Ubuntu 24.04, RTX PRO 6000 Blackwell, CUDA 13.0 —

cmake --preset py3.12 -DCMAKE_BUILD_TYPE=Release -DISAAC_TELEOP_WARNINGS_AS_ERRORS=ON
cmake --build --preset py3.12 --parallel 24 --clean-first

• 328 first-party TUs, zero warnings, clean under -Werror. This covers the targets
  macOS cannot reach: rebot_devarm_leader on its real SocketCAN path (so the
  -Wno-unused-private-field suppression above is confirmed to be needed only off
  Linux), and the whole Televiz tree with BUILD_VIZ auto-ON (Vulkan + CUDA + glslang
  all present).
• BUILD_PLUGIN_OGLO=ON and BUILD_PLUGIN_NOITOM_MOCAP=ON also build clean under
  -Werror.
• ctest: 308/309. The one failure, cloudxr_test_launcher, is the missing CloudXR SDK
  (no NGC key on this host, so the download 404s and get_sdk_path() raises) — the same
  environment gap as on macOS, not a code failure.
• SKIP=check-copyright-year pre-commit run --all-files: all hooks pass.

Known limitation — BUILD_PLUGIN_OAK_CAMERA=ON does not build with
ISAAC_TELEOP_WARNINGS_AS_ERRORS=ON. DepthAI pulls XLink via FetchContent from inside
src/plugins/oak/, so that third-party tree does inherit the flags — 41 errors, all in
xlink-src (16 unused-parameter, 11 stringop-truncation, 5 unused-variable, 3
parentheses, 2 unused-but-set-variable, 2 implicit-fallthrough, 1
unused-but-set-parameter, 1 switch). Note stringop-truncation is a GCC default
rather than part of this warning set, so plain -Werror would break XLink regardless.
This is why ISAAC_TELEOP_WARNINGS_AS_ERRORS defaults to OFF and CI is left at the
default; enabling it in CI needs OAK excluded or a suppression scoped to the fetched
tree. The header comment in cmake/CompilerWarnings.cmake records the gap.

MSVC is unvalidated.

Checklist

• I have read and understood the contribution guidelines
• I have run the linter and formatter with SKIP=check-copyright-year pre-commit run --all-files
• I have made corresponding changes to the documentation
• I have added tests that prove my fix/feature works (or explained why not)
• I have signed off all my commits (git commit -s) per the DCO

Documentation: no user-facing behaviour changes, so no doc updates. The two new CMake
options are documented in the header comment of cmake/CompilerWarnings.cmake.

Tests: no new tests — this is a build-configuration and lint-configuration change, and
it is exercised by the existing suite building and passing under -Werror on both
toolchains above.

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[maxwbuckley]

Superseded by a split into two independent PRs, so the C++ and Python changes can be reviewed separately:

• build: add project C++ warning set with opt-in warnings-as-errors #882 — build: project C++ warning set (CMake + .cpp only)
• chore: configure ruff lint rules and fix what they surfaced #883 — chore: ruff lint rules (pyproject.toml + .py only)

The two commits touch disjoint file sets, so the split is one commit per PR with no rebasing. Closing this one.