Eliminate ~226 redundant source compilations; use ccache and nproc for local builds

[Copilot]

Description

Build times were unnecessarily long because executables recompiled all library source files instead of linking against the already-built shared library. Across 7 packages, this caused ~226 extra .cpp compilations per clean build on top of ~194 unique source files.

Source duplication fixes — executables now target_link_libraries against their package library:

• rj_strategy: 27 src × 5 executables = 135 compilations eliminated
• rj_ui: 18 src × 2 executables = 36 eliminated
• rj_planning: 27 src × 1 executable = 27 eliminated
• rj_vision_filter: 18 src × 1 executable = 18 eliminated
• rj_referee: 3 src × 2 executables = 6 eliminated
• rj_control: 2 src × 1 executable = 2 eliminated
• rj_radio: extracted rj_radio_base shared lib for radio.cpp = 1 eliminated

Before:

add_executable(planner_node
  ${RJ_PLANNING_SRC}   # recompiles all 27 files
  src/main.cpp
)

After:

add_executable(planner_node
  src/main.cpp
)
target_link_libraries(planner_node PRIVATE ${PROJECT_NAME})

CI workflow (ci.yml) — from previous commits on this branch:

• Switched to pre-built robojackets/robocup-software:humble image (skips ubuntu-setup)
• Added actions/cache-backed ccache with -g1 debug symbols
• Shallow clone (fetch-depth: 1)

Makefile:

• Auto-detect ccache and inject --cmake-args for compiler launcher
• Use nproc for local parallel workers instead of hardcoded 4
• docker_ci.yml now rebuilds image on util/ubuntu-setup, ubuntu-packages.txt, requirements3.txt changes

Associated Issue

Build times from scratch are too long, especially in resource-constrained Docker containers.

Steps to test

1. make clean && make all — verify clean build completes with fewer total compilations
2. Check that all executables link and run (e.g. ./install/lib/rj_strategy/kicker_picker_node --help)
3. On a machine with ccache: ccache -s before and after build to confirm cache hits on rebuild

Expected result: Clean build compiles ~194 source files instead of ~420. Rebuild with ccache is near-instant.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.