Support "@ path" file reference (space after @) when file exists

Extend the `o` open-file feature so a reference written with a space
after the @ ("@ path/to/file.txt") is also recognized. Because "@ word"
is common in prose (e.g. "meet @ 5pm"), the spaced form is only treated
as a file reference when the resolved path actually exists on disk. The
original no-space "@path" form keeps precedence and its existing
behavior (opened as-is, so a not-yet-existing file can be created).

Adds fileRefSpacedRegex, a fileExists guard, and unit tests covering the
existing/missing/prose/precedence cases.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

3 files changed, 63 insertions, 6 deletions

diff --git a/internal/ui/fileref_test.go b/internal/ui/fileref_test.go
index 662f5ab..1ab9c06 100644
--- a/internal/ui/fileref_test.go
+++ b/internal/ui/fileref_test.go
@@ -50,6 +50,37 @@ func TestResolveFileRefPathTilde(t *testing.T) {
 	}
 }
 
+// TestExtractFileRefSpaced verifies the "@ path" form: a space after the @ is
+// only treated as a file reference when the resolved path exists on disk, so
+// ordinary "@ word" prose does not false-match.
+func TestExtractFileRefSpaced(t *testing.T) {
+	dir := t.TempDir()
+	existing := filepath.Join(dir, "real.txt")
+	if err := os.WriteFile(existing, []byte("hi"), 0o644); err != nil {
+		t.Fatalf("write temp file: %v", err)
+	}
+	missing := filepath.Join(dir, "nope.txt")
+
+	cases := []struct {
+		name string
+		text string
+		want string
+	}{
+		{"spaced existing file", "please open @ " + existing, existing},
+		{"spaced missing file", "please open @ " + missing, ""},
+		{"spaced prose not a file", "let's meet @ 5pm today", ""},
+		{"no-space form still wins", "@main.go and @ " + existing, "main.go"},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := extractFileRef(tc.text); got != tc.want {
+				t.Fatalf("extractFileRef(%q) = %q, want %q", tc.text, got, tc.want)
+			}
+		})
+	}
+}
+
 // TestFindTaskFileRefFallsBackToAnnotations verifies that the description is
 // scanned first and annotations are used only when the description has no
 // reference.
diff --git a/internal/ui/keyactions.go b/internal/ui/keyactions.go
index a2902a5..871ff05 100644
--- a/internal/ui/keyactions.go
+++ b/internal/ui/keyactions.go
@@ -171,14 +171,35 @@ func findTaskFileRef(t *task.Task) string {
 	return ""
 }
 
-// extractFileRef parses an "@path/to/file.txt" reference out of text and
-// returns the resolved filesystem path (empty when no reference is present).
+// extractFileRef parses a file reference out of text and returns the resolved
+// filesystem path (empty when no reference is present). Two forms are accepted:
+//
+//   - "@path/to/file.txt" (no space) — taken as-is, so a not-yet-existing file
+//     can still be opened/created in the editor.
+//   - "@ path/to/file.txt" (space after @) — only accepted when the resolved
+//     path exists on disk, because "@ word" is common in prose and would
+//     otherwise produce false matches.
+//
+// The no-space form is tried first so it keeps precedence.
 func extractFileRef(text string) string {
-	match := fileRefRegex.FindStringSubmatch(text)
-	if match == nil {
-		return ""
+	if match := fileRefRegex.FindStringSubmatch(text); match != nil {
+		if path := resolveFileRefPath(match[2]); path != "" {
+			return path
+		}
 	}
-	return resolveFileRefPath(match[2])
+	if match := fileRefSpacedRegex.FindStringSubmatch(text); match != nil {
+		if path := resolveFileRefPath(match[2]); path != "" && fileExists(path) {
+			return path
+		}
+	}
+	return ""
+}
+
+// fileExists reports whether path names an existing filesystem entry. It is the
+// guard that disambiguates the "@ path" form from ordinary "@ word" prose.
+func fileExists(path string) bool {
+	_, err := os.Stat(path)
+	return err == nil
 }
 
 // resolveFileRefPath cleans up a raw @-reference path. Trailing punctuation
diff --git a/internal/ui/table.go b/internal/ui/table.go
index 5efb41e..ab71815 100644
--- a/internal/ui/table.go
+++ b/internal/ui/table.go
@@ -36,6 +36,11 @@ var (
 	// "@path/to/file.txt". The leading (^|\s) anchor keeps it from matching
 	// the "@host" part of an email address; capture group 2 is the path.
 	fileRefRegex = regexp.MustCompile(`(^|\s)@(\S+)`)
+	// fileRefSpacedRegex matches the "@ path/to/file.txt" form where a space
+	// follows the @. Because "@ word" is extremely common in prose (e.g.
+	// "meet @ 5pm"), a match here is only treated as a file reference when the
+	// resolved path actually exists on disk; capture group 2 is the path.
+	fileRefSpacedRegex = regexp.MustCompile(`(^|\s)@\s+(\S+)`)
 	// youtubeHostRegex matches the host of a YouTube video link so the "o"
 	// key can route it to an alternative browser. It covers youtube.com (with
 	// optional www./m. subdomains) and the youtu.be short-link domain. Case is