Rank daily-note commands (today first) above other link completions

[Feel-ix-343]

Summary

Typing [today](today or [[today buried the today: <date> daily-note command under every heading whose text happens to contain the word "today" — and in a vault with >20 such headings the daily note was dropped entirely, because run_completer does .take(20) over the matcher's output.

Two causes: sort_text was the raw fuzzy score as a decimal string, so all equally-scoring items (headings and the daily note all scored 140 in a repro vault) got an identical sortText and the client ordered them arbitrarily; and the matcher's output order — which the .take(20) truncation consumes — carried no notion of "this item matters more".

Fix: an explicit priority tier, exposed as a defaulted Matchable::priority() so non-link completables are unaffected:

enum CompletionPriority { Top, Elevated, Normal }   // today | other relative daily notes | everything else

// fuzzy_match_completions
sort by (priority, score desc)
sort_text = format!("{}{:010}", priority as u8, u32::MAX - score)

Zero-padding + inverting the score makes plain lexicographic sortText ordering equal the intended ordering (previously "2" sorted ahead of the better-scoring "21"), and sorting the returned Vec means the .take(20) cut now keeps the daily-note commands instead of cutting them.

MDDailyNote now stores the relative name ("today", "next Monday", …) computed in from_date/from_referenceable instead of re-parsing ref_name against the configured date format, so priority() works without completer context; relative_name() became an infallible &str accessor.

Verified by driving the server over stdio against a vault with 24 headings containing "today": for both [today](today and [[today, today: 2026-08-18 is now item #1 with the smallest sortText (04294967155 vs 24294967155 for the headings), where it previously came back 16th. New matcher unit tests cover tier-beats-score and the sortText lexicographic ordering.

Link to Devin session: https://app.devin.ai/sessions/c57ddce975af4dd5ae7861a1f2205307
Requested by: @Feel-ix-343

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment, CI, and merge conflict monitoring