Remove [[wiki-links]], backlinks and the graph

Operator, 2026-08-22 (note 2897): ThoughtSync is an intermediary surface. You
write here because it's easy — a notebook in your pocket — and later you recall
the thing and go finish it somewhere else. Recall is the product; organization
is secondary. A linking system is organization, and it isn't what this is for.

So: `[[wiki-links]]`, backlinks, the `[[` autocomplete, the note_links table,
`/api/notes/link-search`, `/api/notes/<id>/backlinks`, the whole graph blueprint
and GraphView. Rust core loses `extract_links`, `backlinks`, `link_search` and
`create_titled`; the desktop loses the three Tauri commands that exposed them.

This subsumes 982d24c rather than reverting it. That commit bound links to a
note id so a rename would stop rewriting other notes' bodies — real infra, but
infra for a feature that is now gone, and nothing it added survives. Alembic
0023 stays in the chain anyway: it shipped in an image and may already be
applied, and deleting an applied revision strands a database's version pointer.
0024 drops the table and takes the column with it. The history stays honest
about the fact that it existed for a day.

Two things deliberately kept, because they were serving recall and only
incidentally serving links:

- `/api/notes/titles` and the titles store. The command palette lists them so
  you can jump to a note by name. `resolve()` — the name→note lookup that only
  linking needed — is gone.
- `display_title`. Every note still has a name for search results and export
  filenames. What that name is FOR changed; that it exists did not.

`notes/links.py` is now `notes/tags.py`, holding the #tag→label reconciliation
it always also owned. A file called links.py with no links in it would have been
exactly the drift this removal is meant to end.

Also swept out on the way: `_escape_like`, whose only caller was link-search,
and the `graph` icon. Nothing lost that a person typed — note_links was always
derived, and the `[[text]]` is still sitting in every body it was written in.

core/src/local/derive.rs

@@ -1,38 +1,14 @@
-//! Deriving `[[wiki-links]]` and `#tags` from a note's body — the local mirror of
-//! what the server computes on save. Pure string scanning (no regex dependency),
-//! kept in lockstep with the frontend's inline rules (see frontend notes/markdown.ts):
+//! Deriving `#tags` from a note's body — the local mirror of what the server computes
+//! on save. Pure string scanning (no regex dependency), kept in lockstep with the
+//! frontend's inline rules (see frontend notes/markdown.ts):
 //!
-//! - `[[link]]`: `[[` … `]]` with no brackets inside, inner text trimmed. Used to
-//!   compute backlinks at query time (links are derived, never stored/synced).
 //! - `#tag`: `#` at a word boundary followed by tag characters (letter first).
 //!   On save these become labels attached with `via_tag = true`.
 //!
-//! Both dedupe case-insensitively, preserving first-seen order.
-
-/// Extract the trimmed inner text of every `[[wiki-link]]` in `body`.
-pub fn extract_links(body: &str) -> Vec<String> {
-    let bytes = body.as_bytes();
-    let mut out: Vec<String> = Vec::new();
-    let mut i = 0;
-    while i + 1 < bytes.len() {
-        if bytes[i] == b'[' && bytes[i + 1] == b'[' {
-            if let Some(rel) = body[i + 2..].find("]]") {
-                let inner = &body[i + 2..i + 2 + rel];
-                // Mirror the frontend's `[^[\]]+`: no stray brackets inside.
-                if !inner.contains('[') && !inner.contains(']') {
-                    let t = inner.trim();
-                    if !t.is_empty() {
-                        push_unique(&mut out, t);
-                    }
-                }
-                i += 2 + rel + 2;
-                continue;
-            }
-        }
-        i += 1;
-    }
-    out
-}
+//! Dedupes case-insensitively, preserving first-seen order.
+//!
+//! Also derived `[[wiki-links]]` until they were removed (note 2897) — this is a
+//! capture-and-recall surface, and a linking system is organization.
 
 /// Extract every `#tag` name (without the leading `#`) from `body`.
 pub fn extract_tags(body: &str) -> Vec<String> {
@@ -73,28 +49,6 @@ fn push_unique(out: &mut Vec<String>, candidate: &str) {
 mod tests {
     use super::*;
 
-    #[test]
-    fn links_basic_and_trim() {
-        assert_eq!(
-            extract_links("see [[ Alpha ]] and [[Beta]]"),
-            vec!["Alpha", "Beta"]
-        );
-    }
-
-    #[test]
-    fn links_dedupe_case_insensitive_first_seen() {
-        assert_eq!(extract_links("[[Note]] then [[note]] again"), vec!["Note"]);
-    }
-
-    #[test]
-    fn links_ignore_malformed_and_nested_brackets() {
-        assert_eq!(
-            extract_links("[[a[b]] [[]] [ [x] ] plain"),
-            Vec::<String>::new()
-        );
-        assert_eq!(extract_links("[[ok]] [[a]b]]"), vec!["ok"]);
-    }
-
     #[test]
     fn tags_basic() {
         assert_eq!(
@@ -116,7 +70,6 @@ mod tests {
 
     #[test]
     fn empty_body() {
-        assert!(extract_links("").is_empty());
         assert!(extract_tags("").is_empty());
     }
 }