Remove .md suffix stripping from key lookups

The strip_md_suffix function was removed but its usages remained,
causing lookups like `identity.md` to fail (stripped to `identity`
which didn't exist). Now keys are used as-is.

Renamed 4 nodes that had .md suffixes to canonical form:
- identity.md → identity
- promotion-work-queue.md-* → promotion-work-queue-*
- patterns.md#* → patterns-*
- practices.md#* → practices-*

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/subconscious/digest.rs

@@ -23,16 +23,6 @@ fn normalize_link_key(raw: &str) -> String {
 
     let mut key = key.to_string();
 
-    // Strip .md suffix if present
-    if let Some(stripped) = key.strip_suffix(".md") {
-        key = stripped.to_string();
-    } else if key.contains('#') {
-        let (file, section) = key.split_once('#').unwrap();
-        if let Some(bare) = file.strip_suffix(".md") {
-            key = format!("{}-{}", bare, section);
-        }
-    }
-
     // weekly/2026-W06 → weekly-2026-W06, etc.
     if let Some(pos) = key.find('/') {
         let prefix = &key[..pos];