fix(fmt): apply rustfmt to session.rs test assertions

[Brian Krabach (bkrabach)]

Problem

Rust Core CI has been failing on main since PR #84 (fix(session): emit session:start once per session) merged with admin-override despite a failing Rustfmt step.

Diff in crates/amplifier-core/src/session.rs:797:
             .filter(|(name, _)| name == events::SESSION_START)
             .count();
         assert_eq!(
-            start_count,
-            1,
+            start_count, 1,
             "session:start must fire exactly once per session\u2026"

Diff in crates/amplifier-core/src/session.rs:842:
         assert_eq!(
-            resume_count,
-            1,
+            resume_count, 1,

Fix

cargo fmt -p amplifier-core \u2014 two assertion macros collapse to canonical formatting. Tests behave identically; this is pure whitespace.

Verification (all four CI commands run locally on the fixed branch)

Step	Result
cargo fmt -p amplifier-core -p amplifier-core-py --check	\u2705
cargo check -p amplifier-core -p amplifier-core-py	\u2705
cargo test -p amplifier-core --no-run	\u2705
cargo clippy -p amplifier-core -p amplifier-core-py -- -D warnings	\u2705

Notes

• This is the third PR in this session to hit the Rust Core CI workflow. Worth flagging: PR fix(session): emit session:start once per session, not per execute() — v1.6.0 #84 should have run rustfmt locally before pushing. The earlier push-to-main CI fix (ci: run Rust Core CI on push to main, not just PRs #82) is now active, so future merges will catch this on the merge commit \u2014 but the fault remains that --admin bypass let it through.