chore(comments): drop epic, sprint and review-round ids from the code

The code cited its plan instead of saying why: `E28 review J4`, `(R6 S3b)`, `S1 justified…`,
`deep-review round 5`. That plan lives in the private ops repo, so for every reader of this one the
citation was noise, and a sentence whose subject was the plan step ("round 2 showed…") hid its
lesson behind an id. Each one is gone and the "why" kept: a bare citation is deleted, a sentence
carrying a lesson is reworded around it ("a later attempt showed…").

Measured (`scripts/audit_metrics.py`, product code): 652 lines in 270 files carried an epic code by
the definition the next commit holds (507 / 241 by the old, two-digit-only one) -> 0. Across all
code, tests, scripts and configs: ~1100 epic-code lines plus ~320 sprint/round ids.

Behaviour unchanged, checked mechanically: every changed .py file has the same AST once docstrings
are blanked; css/sh/toml/yml/json files are identical once comments are stripped; the only
non-comment changes in TS/JS are test titles, one description string in a contract table, and five
ESLint messages, whose text is all the gates snapshot diff holds. Not touched: Markdown (docs and
the changelog keep their history), Alembic migrations, TV episode notation (`S2 · E5`), DESIGN.md
ids (`C1`, `B4`, `S3h`), tracker ids (`SEC-16`, `DX-17`).

One stale claim fixed on the way: test_hls_reaper's docstring said the player checkpoints "every
10 s whether or not it is playing", which plex/stream.py calls wrong; it now says what the code does.

backend/app/logs.py

@@ -10,7 +10,7 @@ the logs were both unjoinable and leaky. `configure_logging()` replaces all four
 Event shape — the OpenTelemetry log data model, without the SDK; one JSON object per line:
     ts · level · sev · source · logger · event · msg · attrs
 plus whatever correlation the context carries (`request_id`, `user_id`, `debug_session_id`,
-`job_id`) and the app version. That shape is what E22.6's admin console filters on and what a Gitea
+`job_id`) and the app version. That shape is what the admin log console filters on and what a Gitea
 issue attachment will carry, so it is deliberately flat and stable.
 
 Call sites stay ordinary stdlib logging:
@@ -106,7 +106,7 @@ class _RequestScope:
         self.user_id: int | None = None
         # The user's consented diagnostics level as a logging number; None at the base level.
         self.level: int | None = None
-        # The user's own open debug session this request named (E16), else None.
+        # The user's own open debug session this request named, else None.
         self.debug_session_id: str | None = None
 
 
@@ -122,11 +122,11 @@ def set_user(
     debug_session: str | None = None,
 ) -> None:
     """Attribute the rest of this request's log lines to `user_id`, and log them at the user's
-    consented diagnostics `level` until `until` (E22 S5; "INFO" = no elevation). Called from the
+    consented diagnostics `level` until `until` ("INFO" = no elevation). Called from the
     auth dependency — the one place the session is actually resolved into an account — rather than
     from the request middleware, which runs OUTSIDE the session middleware.
 
-    `debug_session` tags every line with the user's open debug session (E16). The caller has
+    `debug_session` tags every line with the user's open debug session. The caller has
     already checked it is theirs and open; a session's level arrives here as `level`/`until`.
 
     The root logger's floor is tracked per elevation: a request without the session's header (an
@@ -334,7 +334,7 @@ _RECORD_STANDARD = frozenset(
 class ContextFilter(logging.Filter):
     """Copies the correlation contextvars onto the record. A Filter (not the formatter) so the
     values are captured at emit time, before a QueueHandler can move the record to another
-    thread — the DB sink in S3 depends on that."""
+    thread — the DB sink depends on that."""
 
     def filter(self, record: logging.LogRecord) -> bool:
         for name, var in _CONTEXT_VARS.items():
@@ -355,7 +355,7 @@ class ContextFilter(logging.Filter):
 
 class LevelGate(logging.Filter):
     """The configured level, enforced at the HANDLER, with one exception: the lines of a request
-    whose user raised their diagnostics level (E22 S5).
+    whose user raised their diagnostics level.
 
     The root logger's level cannot do this alone: it is one number for the whole process, and the
     point is to log ONE user's requests in detail while everyone else's stay at the base level. So
@@ -457,7 +457,7 @@ class TextFormatter(logging.Formatter):
 # --- configuration -------------------------------------------------------------------------
 # Third-party loggers that are noisy at our own level. Pinned explicitly so the diagnostics knob can
 # lower the ROOT level to DEBUG/TRACE without drowning the output in SQL statements and HTTP chatter
-# — raising THESE is a deliberate, separate act (E22.6's console).
+# — raising THESE is a deliberate, separate act (the admin log console).
 _THIRD_PARTY_LEVELS = {
     "sqlalchemy": "WARNING",
     "sqlalchemy.engine": "WARNING",
@@ -481,7 +481,7 @@ def get_logger(name: str) -> logging.Logger:
     `siftlode.plex.sync`.
 
     The names were literals before, and 25 of them covered 34 modules — six different Plex modules
-    all called themselves `siftlode.plex`, so neither a level pinned per logger nor E22.6's console
+    all called themselves `siftlode.plex`, so neither a level pinned per logger nor the console's
     filter could tell a sync line from a stream line. Derived from `__name__` there is exactly one
     name per module, it cannot drift from the file it sits in, and `test_logger_names.py` fails if a
     module hand-rolls one again.
@@ -562,12 +562,12 @@ def current_level() -> str:
     return logging.getLevelName(_base_level or logging.getLogger().getEffectiveLevel())
 
 
-# --- per-user elevation (E22 S5) -----------------------------------------------------------
+# --- per-user elevation -----------------------------------------------------------
 # The base level (`LOG_LEVEL`, then the admin knob). NOTSET until configure_logging runs — a unit
 # test, a script — so the gate lets everything through there, as it did before the gate existed.
 _base_level = logging.NOTSET
 # → (level number, expiry) for every elevation this process has seen and not yet expired: a user's
-# own, by user id, and a debug session's (E16), by (user id, session id) — its requests alone carry
+# own, by user id, and a debug session's, by (user id, session id) — its requests alone carry
 # its level, so it is tracked apart from the user's own requests.
 _ElevationKey = int | tuple[int, str]
 _elevations: dict[_ElevationKey, tuple[int, datetime]] = {}
@@ -667,7 +667,7 @@ def current_source() -> str:
 
 
 # --- request logging -----------------------------------------------------------------------
-# A client may supply its own request id so a browser log line and a server line join up (E22 S4).
+# A client may supply its own request id so a browser log line and a server line join up.
 # Accepted only in this shape: it ends up in a log field, and an unbounded header would be a way to
 # write arbitrary text into the log.
 _REQUEST_ID_RE = re.compile(r"^[A-Za-z0-9._-]{8,64}$")