docs: add v0.1.1 release notes

[IsuraManchanayake]

Summary

• add the curated user-facing notes for ComputeArena CLI 0.1.1, covering everything merged into rc-0.1.1 since v0.1.0: verifiable model identity and receipts (feat(models): verify runtime-neutral model identity #22, fix(models): stop inventing artifact paths and let the server settle grouping #26), the BaseRT catalogue picker, computearena identify, pre-submission artifact checks, the model-family rule, update notices and HTTP 426 upgrade guidance (feat(cli): negotiate supported client versions #25), and the Linux x86-64 BaseRT notice (fix(basert): explain Linux x86-64 availability #23)
• keep the 0.1.0 structure: install or upgrade, highlights, supported systems, trust boundary, known limitations
• describe the service-side verification outcome conditionally, since it appears once the matching web release is deployed

If #24 (terminal link selection) lands in rc-0.1.1 before the tag, it needs one more bullet: mouse events stay with the terminal so text selection and link clicking work, and mouse-wheel scrolling inside the full-screen interface is replaced by the keyboard.

When v0.1.1 is tagged after the RC reaches main, the release workflow uses docs/release-notes/0.1.1.md as the release body instead of generated notes.

Validation

• .github/scripts/check_version.sh 0.1.1 passes against the workspace version
• release-note file is present and non-empty
• no internal repository names, local paths, or staging hostnames
• git diff --check passes