Use target-specific firmware address data

[ericlewis]

Summary

• Add a shared firmware address table for known 3.0.2 Rev B data.
• Make generate_start.py select version/revision data and fail clearly when missing.
• Make combine.py use the shared table for the Rev B patch location and loader entry address.

Why

Firmware addresses are exact addresses. If the same numbers are copied in many places, one copy can get old or be used for the wrong Playdate version. One table makes that harder and gives a clear error when an address is unknown.

Verification

• python3 -m py_compile generate_start.py combine.py firmware_addresses.py
• python3 generate_start.py --revision A exits with the expected missing-address error
• python3 generate_start.py
• cmake -S . -B /tmp/playbrew-verify-target-specific-addresses
• cmake --build /tmp/playbrew-verify-target-specific-addresses
• git diff --check

[ericlewis]

Replaced by #11 with the cleaned branch name.