chore(wrapper): verify Muskingum_V and DistMaxbas1 are correct for lake routing

[MAfarrag]

Context

PR #149 fixed two `AttributeError` bugs in `wrapper.py` where
nonexistent methods were called:

• `routing.muskingum()` → `routing.Muskingum_V()`
• `distrrm.DistMAXBAS()` → `distrrm.DistMaxbas1()`

The old methods never existed, so the `FW1Withlake` code path was
always broken. The fix chose the closest matching methods, but the
specific variants should be verified.

Problem / Current Behaviour

`Muskingum_V` is the vectorized variant (clamps negative outflow).
`Muskingum` is the iterative variant. The choice matters for model
results. Similarly, `DistMaxbas1` vs `DistMaxbas2` use different
spatial weighting strategies.

Affected locations

File	Symbol	Notes
`src/Hapi/wrapper.py:~275`	`FW1Withlake`	Uses `Muskingum_V`
`src/Hapi/wrapper.py:~286`	`FW1Withlake`	Uses `DistMaxbas1`

Proposed Solution

1. Confirm with domain knowledge whether `Muskingum_V` (vectorized)
   or `Muskingum` (iterative) is correct for lake outflow routing
2. Confirm whether `DistMaxbas1` or `DistMaxbas2` is correct for
   the FW1 framework
3. Add a brief comment explaining the choice
4. Add integration test covering the `FW1Withlake` code path

Effort Estimate

Size: `S`
Rationale: Domain verification + one comment + one test.

Definition of Done

• Routing method choice confirmed and documented with a comment
• Integration test covers the `FW1Withlake` execution path
• Test verifies no `AttributeError` and produces reasonable output

[MAfarrag]

Closed: created in error. These are follow-up items from PR #152 review, not standalone issues.