Remove assertions from non-test code

[s2t2]

Let's remove all the assertions from non-test code. For example the ones occurring in smart_control/simulator/stochastic_occupancy.py.

"Do not use assert statements in place of conditionals or validating preconditions." - source

Originally posted by @s2t2 in #27 (comment)

Instead, we should raise errors like ValueError, etc.

[igopalakrishna]

I've just submitted PR #109 to fix the assertions in the first file. I'm happy to continue and fix the remaining files for this issue once the initial PR is reviewed. Please let me know if you have any feedback or a preferred way to handle the rest of the changes (e.g., one single PR for all files).

[igopalakrishna]

@s2t2 Quick updates:

1. Fixed CI failures caused by exception-type mismatch: updated boiler_test.py and vav_test.py to expect ValueError (instead of AssertionError).

2. Added unit tests to explicitly trigger each new ValueError validation path introduced in smart_control/ (where applicable), improving coverage for invalid-input branches.

3. Cleaned up several error messages:

   • Wrapped long strings to avoid line-too-long
   • Reworded a few to be more natural-language (esp. arrival/departure ordering) while keeping messages deterministic for tests.

Testing: Ran the full suite using the same flow as GitHub Actions (poetry and pytest) - 684 passed, 38 skipped.

Note: I also attempted running the suite in Docker, but dependency installation fails on Linux due to dm-reverb wheel availability, so the container never reaches pytest. Since CI doesn’t use Docker, the poetry-based run above should be the relevant signal.

Changes are ready for review on the PR branch. Thank you!