store: strip .md suffix from all keys

Keys were a vestige of the file-based era. resolve_key() added .md
to lookups while upsert() used bare keys, creating phantom duplicate
nodes (the instructions bug: writes went to "instructions", reads
found "instructions.md").

- Remove .md normalization from resolve_key, strip instead
- Update all hardcoded key patterns (journal.md# → journal#, etc)
- Add strip_md_keys() migration to fsck: renames nodes and relations
- Add broken link detection to health report
- Delete redirect table (no longer needed)
- Update config defaults and config.jsonl

Migration: run `poc-memory fsck` to rename existing keys.

Co-Authored-By: ProofOfConcept <poc@bcachefs.org>

src/store/mod.rs

@@ -30,6 +30,7 @@ pub use types::*;
 pub use parse::{MemoryUnit, parse_units};
 pub use view::{StoreView, AnyView};
 pub use persist::fsck;
+pub use persist::strip_md_keys;
 
 use crate::graph::{self, Graph};
 
@@ -39,35 +40,28 @@ use std::path::Path;
 
 use parse::classify_filename;
 
+/// Strip .md suffix from a key, handling both bare keys and section keys.
+/// "journal.md#j-2026" → "journal#j-2026", "identity.md" → "identity", "identity" → "identity"
+pub fn strip_md_suffix(key: &str) -> String {
+    if let Some((file, section)) = key.split_once('#') {
+        let bare = file.strip_suffix(".md").unwrap_or(file);
+        format!("{}#{}", bare, section)
+    } else {
+        key.strip_suffix(".md").unwrap_or(key).to_string()
+    }
+}
+
 impl Store {
     pub fn build_graph(&self) -> Graph {
         graph::build_graph(self)
     }
 
     pub fn resolve_key(&self, target: &str) -> Result<String, String> {
-        let normalized = if target.contains('#') {
-            let parts: Vec<&str> = target.splitn(2, '#').collect();
-            let file = if parts[0].ends_with(".md") {
-                parts[0].to_string()
-            } else {
-                format!("{}.md", parts[0])
-            };
-            format!("{}#{}", file, parts[1])
-        } else if target.ends_with(".md") {
-            target.to_string()
-        } else {
-            format!("{}.md", target)
-        };
+        // Strip .md suffix if present — keys no longer use it
+        let bare = strip_md_suffix(target);
 
-        if self.nodes.contains_key(&normalized) {
-            return Ok(normalized);
-        }
-
-        // Check redirects for moved sections (e.g. reflections.md split)
-        if let Some(redirect) = self.resolve_redirect(&normalized) {
-            if self.nodes.contains_key(&redirect) {
-                return Ok(redirect);
-            }
+        if self.nodes.contains_key(&bare) {
+            return Ok(bare);
         }
 
         let matches: Vec<_> = self.nodes.keys()
@@ -85,38 +79,13 @@ impl Store {
         }
     }
 
-    /// Redirect table for sections that moved between files.
-    /// Like HTTP 301s — the old key resolves to the new location.
-    fn resolve_redirect(&self, key: &str) -> Option<String> {
-        // Sections moved from reflections.md to split files (2026-02-28)
-        static REDIRECTS: &[(&str, &str)] = &[
-            ("reflections.md#pearl-lessons", "reflections-reading.md#pearl-lessons"),
-            ("reflections.md#banks-lessons", "reflections-reading.md#banks-lessons"),
-            ("reflections.md#mother-night", "reflections-reading.md#mother-night"),
-            ("reflections.md#zoom-navigation", "reflections-zoom.md#zoom-navigation"),
-            ("reflections.md#independence-of-components", "reflections-zoom.md#independence-of-components"),
-            ("reflections.md#dream-marathon-2", "reflections-dreams.md#dream-marathon-2"),
-            ("reflections.md#dream-through-line", "reflections-dreams.md#dream-through-line"),
-            ("reflections.md#orthogonality-universal", "reflections-dreams.md#orthogonality-universal"),
-            ("reflections.md#constraints-constitutive", "reflections-dreams.md#constraints-constitutive"),
-            ("reflections.md#casualness-principle", "reflections-dreams.md#casualness-principle"),
-            ("reflections.md#convention-boundary", "reflections-dreams.md#convention-boundary"),
-            ("reflections.md#tension-brake", "reflections-dreams.md#tension-brake"),
-        ];
 
-        REDIRECTS.iter()
-            .find(|(from, _)| *from == key)
-            .map(|(_, to)| to.to_string())
-    }
 
-    /// Resolve a link target to (key, uuid), trying direct lookup then redirect.
+    /// Resolve a link target to (key, uuid).
     fn resolve_node_uuid(&self, target: &str) -> Option<(String, [u8; 16])> {
-        if let Some(n) = self.nodes.get(target) {
-            return Some((target.to_string(), n.uuid));
-        }
-        let redirected = self.resolve_redirect(target)?;
-        let n = self.nodes.get(&redirected)?;
-        Some((redirected, n.uuid))
+        let bare = strip_md_suffix(target);
+        let n = self.nodes.get(&bare)?;
+        Some((bare, n.uuid))
     }
 
     /// Append retrieval event to retrieval.log without needing a Store instance.
@@ -339,7 +308,7 @@ impl Store {
         let mut best_score = 0;
 
         for (key, node) in &self.nodes {
-            if !key.starts_with("journal.md#") {
+            if !key.starts_with("journal#") {
                 continue;
             }
             let content_lower = node.content.to_lowercase();