theboringoffice v0.2.30 — freeze keeps the chain

Fixes the base64-text leak members saw when re-opening the browser tab on v0.2.29.

Root cause: the keep-alive freeze SIGSTOPs the child mid-chunk constantly; resetting the splitter dropped the chain's head, so the thawed tail (pure base64, no escape opener) painted as text. Freeze now parks consumption only — the pending chain is preserved and the thawed tail completes it into a valid frame. Proven across 40 forced mid-chain freezes with zero base64 on grid or scrollback, and mutation-tested by restoring the old behavior (which reproduces the exact rows from the member's screenshot).

Also adds cmd/kittyprobe: a tiny diagnostic that asks your terminal which kitty frame shapes it accepts (the terminal answers in its own words) — built for the ongoing empty-pane investigation.

Full Changelog: v0.2.29...v0.2.30