chore: scrub #NNN issue references from code comments and nix descriptions

Part of the docs-migration chore (issue #708). Remove GitHub issue
numbers from inline comments, option descriptions, and rustdoc —
these are contextless noise for anyone reading the code without
access to the original discussions. Replace with prose that captures
the same rationale directly.

No functional change. Build still clean (cargo check passes).

hive-c0re/src/limits.rs

@@ -50,7 +50,7 @@ pub fn check_size(label: &str, body: &str) -> Result<(), String> {
 /// scrolling chunk.
 pub const STATUS_MAX_CHARS: usize = 200;
 
-/// Validate a `set_status` payload (#720). Single-line + bounded so
+/// Validate a `set_status` payload. Single-line + bounded so
 /// callers can't dump multi-paragraph session reports into the
 /// dashboard chip. Whitespace trim is done by the caller before the
 /// store-to-disk step — we run validation on the trimmed form so
@@ -70,8 +70,7 @@ pub fn check_status_text(text: &str) -> Result<(), String> {
         return Ok(());
     }
     // Newline / carriage-return: status is a single-line chip on the
-    // dashboard. A multi-line argus session report is the canonical
-    // failure mode from #720.
+    // dashboard. Multi-line session reports should go to a state file.
     if trimmed.contains('\n') || trimmed.contains('\r') {
         return Err(
             "set_status text must be a single line — write multi-line context to \