test: end-to-end go-to-definition for wikilinks with periods in filenames

[Feel-ix-343]

Summary

Adds an end-to-end go-to-definition regression test for wikilinks whose target contains a period (e.g. [[CandS Exa 3 v9.1 Repro Rerun|9.1]]). The fix for this already landed on main in 52aa8ac3 ("Fix go-to-definition for files with dots in names", issue Feel-ix-343#344), which dropped \. from the WIKI_LINK_RE filepath class. But every test that commit added asserts only parsing via Reference::new; none exercise the full LSP resolution path. This adds that missing coverage so a future regex/parser change can't silently re-break gd on dotted filenames.

Why it matters: the WIKI_LINK_RE pattern has been rewritten 5× in this file's history, and a parse-only test does not catch a regression in the parse → Referenceable matching → Location chain that gotodef::goto_definition actually walks.

The test builds a real Vault from a temp dir and asserts gd resolves to the dotted file:

// note.md: "- [[CandS Exa 3 v9.1 Repro Rerun|9.1]] reproduces results"
// + file:  "CandS Exa 3 v9.1 Repro Rerun.md"
let vault = Vault::construct_vault(&settings, &dir)?;
let locations = goto_definition(&vault, Position { line: 2, character: 10 }, &note)
    .expect("gd returned None for a period-containing wikilink");
assert!(locations.iter().any(|l| l.uri.to_file_path()? == target));

Verification: full suite cargo test passes; cargo fmt --check clean; cargo clippy --tests adds no new warnings.

Note: this is test-only — no production change. The underlying fix is on main but unreleased (latest tag v0.25.10 predates 52aa8ac3), so a release is what ships it to editors.

Link to Devin session: https://app.devin.ai/sessions/a634af9155e846ac82fa63a8f57f35ab
Requested by: @Feel-ix-343

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[devin-ai-integration]

Runtime test: go-to-definition on period-containing wikilinks

Tested in Helix on a vault with the exact note scenario (- [[CandS Exa 3 v9.1 Repro Rerun|9.1]] + the target file CandS Exa 3 v9.1 Repro Rerun.md). Same file, same cursor (5:18, on the 9 in v9.1), same keypress (g d) — the only variable between phases is the markdown-oxide binary.

• It should fail gd on a period wikilink (pre-fix 52aa8ac3~1): passed — status line shows No definition found.
• It should resolve gd on a period wikilink (fixed main): passed — gd opens CandS Exa 3 v9.1 Repro Rerun.md.

Before / after (click images to enlarge)

🔴 Pre-fix binary (52aa8ac3~1)	🟢 Fixed binary (main / 52aa8ac3)
g d → red "No definition found.", buffer stays on PeriodLinkTest.md	g d → editor opens CandS Exa 3 v9.1 Repro Rerun.md

Recording (both phases)

Cross-checks

• Bisect: 52aa8ac3~1 → gd resolves false; 52aa8ac3 → true. The commit is exactly the turning point.
• Real agent-knowledge vault: on main, gd on both period links in 2026-06-10.md resolves; neither is flagged as an Unresolved Reference diagnostic.
• Unit: cargo test 76/76 pass, cargo fmt --check clean, cargo clippy --tests no new warnings.
• Note: the fix is on main but unreleased (latest tag v0.25.10 predates 52aa8ac3); a release ships it to editors. This PR is test-only.

Tested by Devin — session: https://app.devin.ai/sessions/a634af9155e846ac82fa63a8f57f35ab