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>

README.md

@@ -13,12 +13,12 @@ and emit; their records flow into the handlers `log_setup` wired.
 ## Install
 
 ```
-log_setup @ git+ssh://git@git.rethinkstudios.io/rethink-public/log_setup.git@v0.3.2
+log_setup @ git+ssh://git@git.rethinkstudios.io/rethink-public/log_setup.git@v0.4.0
 ```
 
 No dependencies — stdlib only.
 
-Drop the `@v0.3.2` suffix from the line above to install the latest unpinned.
+Drop the `@v0.4.0` suffix from the line above to install the latest unpinned.
 
 ## Quick start
 
@@ -50,10 +50,49 @@ emits; the records land in the configured root.
     (`run.<timestamp>.log[.gz]`) and starts fresh; prunes to `backup_count`.
   - `None` — single file, no rotation.
 - **compress=True** (default) gzips each rolled file (`run.log.2026-06-27.gz`).
-- **Retention** = `backup_count` (default 14) for every mode.
+- **Retention** = `backup_count` (default 14) for every mode — unless tiered retention is
+  enabled (below).
 - **console=True** (off by default) also logs to stdout in the same format — opt in when
   you want live terminal output alongside the file.
 
+The `name` you pass is normalized so it produces exactly one `.log`: `name="latest"` and
+`name="latest.log"` both yield the live file `latest.log` (never `latest.log.log`).
+
+## Tiered retention (`keep_uncompressed` / `keep_compressed`)
+
+The default is a flat `backup_count`: every rolled file is gzipped on roll and the oldest
+are deleted past the count. If instead you want the recent logs **uncompressed** (read them
+without `zcat`) and older ones **gzipped**, pass the two tier knobs:
+
+```python
+setup_logging(
+    name="latest",
+    rotate="on_start",        # works for on_start, daily, and size
+    keep_uncompressed=3,      # newest 3 rolled logs kept PLAIN
+    keep_compressed=7,        # next 7 kept GZIPPED; total retained = 10
+)
+```
+
+Result in `log_dir` (newest → oldest):
+
+```
+latest.log                       <- live "latest" (stable, tail -f)
+latest.<t1>.log   latest.<t2>.log   latest.<t3>.log       <- 3 newest: plain
+latest.<t4>.log.gz ... latest.<t10>.log.gz                 <- next 7: gzipped
+(anything past 10 deleted)
+```
+
+- Each restart (`on_start`) or roll (`daily`/`size`) moves the live file into `log_dir`,
+  then re-tiers: newest `keep_uncompressed` stay plain, the next `keep_compressed` are
+  gzipped in place, the rest deleted. Total kept = `keep_uncompressed + keep_compressed`.
+- **Opt-in by presence** — pass either knob to enable tiering. Pass **neither** and
+  rotation behaves exactly as before (`backup_count` + gzip-on-roll), so existing callers
+  are unaffected.
+- In tiered mode `backup_count` and the gzip-on-roll behavior of `compress` are **ignored**
+  — the tier counts bound retention instead.
+- `keep_uncompressed=0` → everything gzipped; `keep_compressed=0` → only the plain tier.
+  Retention is count-based (not time-based).
+
 ## Output format (`output=`)
 
 Two formats, two needs. Default is `"text"`; the live-file name is the same either way
@@ -94,7 +133,9 @@ setup_logging(
     level="INFO",             # root level everything inherits (str name or logging constant)
     module_levels=None,       # {logger_name: level} per-logger overrides (exact name match)
     rotate="daily",           # "daily" | "size" | "on_start" | None
-    backup_count=14,          # rotated files to keep (older auto-deleted)
+    backup_count=14,          # rotated files to keep (flat retention; ignored if tiered)
+    keep_uncompressed=None,   # tiered: newest N rolled logs kept PLAIN (opt-in)
+    keep_compressed=None,     # tiered: next M rolled logs kept GZIPPED (opt-in)
     max_bytes=10_000_000,     # only for rotate="size"
     compress=True,            # gzip rolled files
     console=False,            # also log to stdout (off by default; opt in)