1.2.5

A performance and footprint release. There are no behavior or configuration
changes: every schedule fires exactly as before, the metrics endpoint renders
byte-for-byte identically, and the core install stays zero-new-dependency. The
work trims CPU on the daemon's hottest repeating paths -- the once-a-minute
config reload, every Prometheus scrape, and each cluster poll / gossip round /
lease renew -- lowers steady-state memory, and adds an optional faster event
loop.

• Optional uvloop event loop (speedups extra). pip install yacron2[speedups] swaps asyncio's selector loop for uvloop's faster
  libuv-based one, speeding every I/O path yacron2 drives: cluster gossip and
  lease HTTP, the web dashboard, and the Prometheus scrape. It is entirely
  opt-in and best-effort -- __main__ selects uvloop lazily on POSIX and falls
  back to stock asyncio, behavior unchanged, whenever it is absent or
  unimportable -- so it stays off the core install to keep the baseline
  architecture-portable. Windows always uses its Proactor loop (there is no
  uvloop build there, and the Proactor loop is required for subprocess support
  anyway). The prebuilt POSIX binaries now bundle uvloop wherever it builds: a
  wheel where one exists, an otherwise verified source build, with a start-up
  self-test (verify_uvloop.py) that uninstalls a miscompiled build (a real
  risk under QEMU emulation) before freezing so the binary cleanly runs on
  asyncio instead. An arch where uvloop cannot build ships the asyncio binary
  exactly as before.

• The once-a-minute reload no longer reparses an unchanged config. The
  scheduler rereads and reparses the config every minute so an on-disk edit is
  picked up promptly, but strictyaml is a slow pure-Python parser and reparsing
  an unchanged file was pure wasted work (in a worker thread, but still real CPU
  plus thread-pool churn). reload_config now compares a cheap os.stat
  fingerprint -- (path, mtime_ns, size) per file, plus the config directory's
  own mtime -- of exactly the files the last parse read (the top-level config,
  every transitively included file, and each job's env_file) and skips the
  reparse entirely when nothing has changed, returning the already-loaded
  config. A genuine edit, a vanished file, or a new entry dropped into a config
  directory still reparses on the next pass.

• Cheaper Prometheus scrapes. The job-set fingerprint (job_set_id, queried
  on every scrape and every cluster poll / gossip round / lease renew) is a pure
  function of the loaded jobs, so it is now computed once per reload and
  memoized rather than re-deriving its per-job deepcopy / JSON / SHA-256 each
  time. The job_next_run_timestamp gauge reads the scheduler's authoritative
  next-fire index instead of re-walking every crontab and building two aware
  datetimes per job per scrape (falling back to a direct computation only in the
  brief start-up window before the index is seeded). The histogram le label
  strings are precomputed once from the bucket bounds rather than re-rendered for
  every bucket of every job on every scrape.

• Lower steady-state memory and faster attribute access. JobConfig -- one
  instance per configured job for the life of the process -- now declares
  __slots__, trimming its per-instance __dict__ and speeding the attribute
  reads on the scheduling hot path. Fingerprint redaction is now copy-on-write
  instead of deepcopy, so the long immutable report templates (the sentry body,
  the webhook body) are shared by reference rather than duplicated on each
  fingerprint. The PyInstaller binaries are now built with optimize=2, which
  strips docstrings and (side-effect-free, internal-invariant) asserts from the
  frozen bytecode -- yacron2's modules are deliberately docstring-dense, so this
  shrinks the binary and lowers resident memory for the life of the daemon.

• The idle scheduler no longer polls once a second. The job reaper waited on
  its "any job running?" event with a one-second timeout, waking every second
  even when nothing was running. It now blocks on the event outright -- the wait
  condition can only change when a job launches or shutdown is signalled, both of
  which set the event (shutdown now does so explicitly, so the reaper exits
  promptly) -- so a fully idle daemon does no per-second work. A related fix reads
  the running-jobs map with .get() so a concurrency check can no longer leave a
  phantom empty entry that would spin the reaper hot at shutdown.

• Internal: the reload skip cache (change detection, the failed-parse and
  worker-thread paths), the memoized fingerprint, and the scrape reading the
  seeded next-fire index are covered by new tests; the uvloop bundling is gated
  behind a build-time verification step and the per-arch --version smoke test.

Full Changelog: 1.2.4...1.2.5