feat: tiered restart/retention (keep_uncompressed/keep_compressed) + name normalize

- keep_uncompressed/keep_compressed: newest N rolled logs plain, next M gzipped, rest
  deleted. applies to on_start/daily/size. opt-in by knob presence; without them the
  legacy backup_count + gzip-on-roll path is unchanged (existing consumers unaffected).
- _normalize_name: 'latest' and 'latest.log' both -> live latest.log (no .log.log).
- _gzip_file preserves source mtime (stable tier ordering across re-tiers).
- rotate_on_start collision counter checks both .log and .log.gz (no duplicate logical
  roll when a same-stamp file was already compressed).

execute-verified stdlib-only incl. a back-compat control proving the no-knobs path is
unchanged. bump v0.3.2 -> v0.4.0

Signed-off-by: disqualifier <dev@disqualifier.me>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "log_setup"
-version = "0.3.2"
+version = "0.4.0"
 description = "stdlib app-entry-point logging setup: live run.log, rotation, gzip, retention, consistent format"
 requires-python = ">=3.10"
 dependencies = []