chore(deps): update rust to nightly-2026-09-20

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
rust (source, changelog)	toolchain	patch	nightly-2026-08-02 → nightly-2026-09-20

---

Configuration

📅 Schedule: (in timezone Asia/Shanghai)

• Branch creation
  • "before 10am on monday"
• Automerge
  • At any time (no schedule defined)

🚦 Automerge: Enabled.

♻ Rebasing: Whenever PR is behind base branch, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

---

• If you want to rebase/retry this PR, check this box

---

This PR was generated by Mend Renovate. View the repository job log.

[github-actions]

fspy benchmark

linux

dynamic/launch             change  +0.19%  [ -7.01% ..  +7.06%]  overhead  +255.33%
dynamic/access             change  +1.54%  [ +0.46% ..  +2.52%]  overhead   +13.77%
dynamic/access-relative    change  +0.77%  [ +0.11% ..  +1.68%]  overhead   +62.84%
dynamic/access-contended   change  +1.15%  [ -0.81% ..  +2.70%]  overhead   +14.17%
static/launch              change  -0.52%  [ -5.79% ..  +5.70%]  overhead  +741.49%
static/access              change  +0.04%  [ -0.57% ..  +0.85%]  overhead  +835.82%
static/access-relative     change  +0.24%  [ -0.76% ..  +1.19%]  overhead +1425.68%
static/access-contended    change  -0.06%  [ -0.83% ..  +0.55%]  overhead +3259.92%

macos

dynamic/launch             change  -0.19%  [ -8.10% ..  +8.43%]  overhead  +239.66%
dynamic/access             change  -0.56%  [-55.34% .. +88.36%]  overhead    +2.68%
dynamic/access-relative    change  -0.89%  [ -8.85% ..  +7.01%]  overhead  +272.70%
dynamic/access-contended   change  +3.28%  [-12.01% .. +752.22%]  overhead    +2.39%

windows