fix(logging): enforce single-writer sinks and bound tracing (#4765)

* fix(obs): prevent rolling log stdout aliasing

* fix(ecstore): bound hot-path tracing payloads

* test(logging): guard service and disk log invariants

* fix(obs): silence useless_conversion on st_dev for Linux clippy

rustix's Stat.st_dev is u64 on Linux/glibc, making u64::try_from a no-op
that trips clippy::useless_conversion under -D warnings. The conversion is
still needed on macOS/BSD where st_dev is a signed dev_t, so suppress the
lint on that line rather than dropping the portable fallible conversion.

* fix(logging): keep stdout sink validation portable (#4769)

* fix(obs): keep stdout device conversion portable

* docs(logging): update single-writer plan status

---------

Co-authored-by: overtrue <anzhengchao@gmail.com>
Co-authored-by: houseme <housemecn@gmail.com>

crates/obs/src/error.rs

@@ -68,6 +68,8 @@ pub enum TelemetryError {
     Io(String),
     #[error("Set permissions failed: {0}")]
     SetPermissions(String),
+    #[error("Log sink conflict: {0}")]
+    LogSinkConflict(String),
 }
 
 impl From<std::io::Error> for TelemetryError {