The daemon and native-runtime SafeFileName copies sanitised differently:
the daemon mapped a/b, a b, a:b and a-b to the same name (a later patch
overwrote an earlier artifact) and returned ".." unchanged, so a
sessionId or runId of ".." resolved one directory above the store.

Replace both with AquaSynth.Dsl.StoreFileName.From. Ids within
[A-Za-z0-9._-] pass through; any other id is sanitised and suffixed with
the first 8 hex of SHA-256 of the original. Empty, "." and all-dot ids
are refused (ArgumentException).

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

@@ -0,0 +22,4 @@
+        var builder = new StringBuilder(id.Length);
+        foreach (var c in id)
+        {
+            builder.Append(c is >= 'a' and <= 'z' or >= 'A' and <= 'Z' or >= '0' and <= '9' or '-' or '_' or '.' ? c : '_');

@@ -0,0 +27,4 @@
+
+        var safe = builder.ToString();
+        // A trailing dot is dropped by Windows, so "a." would alias "a"; hash it like any other rewrite.
+        if (safe == id && !id.EndsWith('.'))

@@ -0,0 +29,4 @@
+        // A trailing dot is dropped by Windows, so "a." would alias "a"; hash it like any other rewrite.
+        if (safe == id && !id.EndsWith('.'))
+        {
+            return safe;

@@ -0,0 +33,4 @@
+        }
+
+        var hash = Convert.ToHexString(SHA256.HashData(Encoding.UTF8.GetBytes(id)))[..8].ToLowerInvariant();
+        return $"{safe}-{hash}";

@@ -0,0 +5,4 @@
+public sealed class StoreFileNameTests
+{
+    [Fact]
+    public void DistinctIdsGetDistinctNames()

@@ -0,0 +59,4 @@
+        using var service = new AquaSynthDaemonService(new AquaSynthDaemonOptions(storeRoot));
+
+        await service.SampleAsync(new AquaSynthInstrumentSampleCommand(
+            "../../escape", "test.invalid", "test_invalid", "this is not aqua syntax", DurationSeconds: 0.1f));