fix: preserve float values in retry backoff config

[steve-calvert-glean]

Summary

• Removes int() truncation in _build_retry_config() that silently corrupted sub-second values
• GLEAN_RETRY_INITIAL=0.5 now correctly rounds to 1 instead of truncating to 0
• Also removes unused import re (dead code)

Root Cause

initial_interval = int(initial) truncates any float < 1.0 to zero, disabling the initial backoff. BackoffStrategy requires int types, so round() is used to preserve intent (0.5 → 1, not 0).

Fixes

CHK-002 from EVAL-CHECKLIST.md (also cleans up CHK-028)

Test plan

• uv run pytest tests/ -x -q passes
• Setting GLEAN_RETRY_INITIAL=0.5 results in a non-zero interval

[steve-calvert-glean]

Code Review — CHK-002

Acceptance Criteria Met

• int() truncation is removed from all three variables: initial_interval, max_interval, max_elapsed_time
• round() is used in place of int() — this is the correct choice per the acceptance criteria
• The dead import re is removed (also cleans up CHK-028 as noted in the PR)
• Change is minimal and focused — only _common.py is modified

Issues Found

• round() still converts floats to ints, which means the fix is a behavior improvement (0.5 rounds to 1 instead of truncating to 0) but does not fully "preserve" float values as the PR title says. This is fine if BackoffStrategy requires int types — the PR description acknowledges this: "BackoffStrategy requires int types, so round() is used to preserve intent". Confirm that BackoffStrategy.initial_interval, max_interval, and max_elapsed_time are typed as int in the SDK; if they accept float directly, round() is still safe but the comment in the description would need updating.
• The exponent field is correctly left as a float (passed directly to BackoffStrategy), confirming the SDK does accept floats for at least one field. This inconsistency in the SDK's type surface is worth a comment in the code so future maintainers don't wonder why exponent is float while the others use round().
• _parse_retry_env_int (lines 68-75 of _common.py) is now dead code — nothing calls it after this change. It's not a blocker, but it's orphaned and should be removed in a follow-up.

Suggestions

• Add a brief inline comment near the round() calls explaining why: # BackoffStrategy requires int; round() preserves intent (e.g. 0.5 → 1, not 0)
• Track removal of _parse_retry_env_int as a follow-up cleanup item.

Verdict: Ready to merge