fix(csv): accept decoded time drum units in round-trip

[GruppoVeneta]

Summary

Allow CSV parsing and writer round-trip validation to accept every time-drum unit that the binary decoder can already emit (Tms, Ts, Tm, Th, and Td).

Previously, parse_af_call() validated units against _TIME_FC, which only contains the units whose binary function codes are currently implemented. As a result, exporting a CLICK program containing a time drum in seconds, minutes, or hours failed during CSV round-trip validation with:

CSV round-trip validation failed: emitted rows do not reparse:
Unsupported time drum unit: 'Ts'

The CSV parser does not build a binary blob, so it now validates against _DRUM_UNIT_TO_INDEX. Binary encoding remains conservative: _compute_func_codes() still rejects units without known function codes.

Tests

• Added parser coverage for all five known time-drum units.
• Preserved rejection of unknown units.
• Added writer round-trip coverage for Ts, Tm, and Th.
• Focused CSV suite: 146 passed.
• Full upstream suite: 695 passed.
• Ruff and git diff --check: passed.

The issue was reproduced from a real CLICK program export using ClickNick 0.19.3 / laddercodec 0.1.8.

[ssweber]

Thanks! I’ll take a look at this in the next day or so and probably merge.