chore(bench): migrate dispatch harness from iai-callgrind to gungraun

iai-callgrind is unmaintained; gungraun is the active fork. API is
drop-in (use iai_callgrind → use gungraun, same library_benchmark /
library_benchmark_group / main! macros), so the dispatch.rs body only
needed the import rename.

Also:
- mise.toml: add cargo:gungraun-runner dep so the valgrind harness
  binary tracks the lib version automatically.
- baseline.txt: rebaselined under gungraun_initial. Absolute numbers
  shifted up because gungraun's bench wrapper instruments more than
  iai-callgrind 0.16's did; comparable benches (terminate_event 69→68,
  h8_cross_tree 93→97) confirm HSM dispatch work itself is unchanged.
  Old iai-callgrind named baselines kept as historical context only.

Cargo.lock

@@ -242,6 +242,43 @@ version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0cc23270f6e1808e30a928bdc84dea0b9b4136a8bc82338574f23baf47bbd280"
 
+[[package]]
+name = "gungraun"
+version = "0.18.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3bfa183cef2c88324b20de9727befd262c35592d9885ffd93b8b102536a81cf2"
+dependencies = [
+ "bincode",
+ "derive_more",
+ "gungraun-macros",
+ "gungraun-runner",
+]
+
+[[package]]
+name = "gungraun-macros"
+version = "0.8.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e35c7fb6133421db1cf752b7a2838d9277a26810ccaeeca7aa449f96ad7c2b01"
+dependencies = [
+ "derive_more",
+ "proc-macro-error2",
+ "proc-macro2",
+ "quote",
+ "rustc_version",
+ "serde",
+ "serde_json",
+ "syn",
+]
+
+[[package]]
+name = "gungraun-runner"
+version = "0.18.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2ebdac6d5fe0aa9d9623d690fbfdb759e0ed44115e0685b9abc4568fe47db364"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "hash32"
 version = "0.3.1"
@@ -285,9 +322,9 @@ dependencies = [
  "embassy-futures",
  "embassy-sync",
  "embassy-time",
+ "gungraun",
  "heapless 0.8.0",
  "hsmc-macros",
- "iai-callgrind",
  "log",
  "tokio",
  "tracing",
@@ -313,42 +350,6 @@ dependencies = [
  "hsmc",
 ]
 
-[[package]]
-name = "iai-callgrind"
-version = "0.16.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0b1e4910d3a9137442723dfb772c32dc10674c4181ca078d2fd227cd5dce9db0"
-dependencies = [
- "bincode",
- "derive_more",
- "iai-callgrind-macros",
- "iai-callgrind-runner",
-]
-
-[[package]]
-name = "iai-callgrind-macros"
-version = "0.6.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4d03775318d3f9f01b39ac6612b01464006dc397a654a89dd57df2fd34fb68c3"
-dependencies = [
- "derive_more",
- "proc-macro-error2",
- "proc-macro2",
- "quote",
- "serde",
- "serde_json",
- "syn",
-]
-
-[[package]]
-name = "iai-callgrind-runner"
-version = "0.16.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b74c9743c00c3bca4aaffc69c87cae56837796cd362438daf354a3f785788c68"
-dependencies = [
- "serde",
-]
-
 [[package]]
 name = "indexmap"
 version = "2.14.0"