Specification: pane.wait_for_output and pane.clear

Created: 2026-10-10. Status: clarified.

herdr scripts can block until a pane prints a line and can clear a pane. signaltty clients must poll pane.read for the first and cannot do the second at all.

Acceptance

1. pane.wait_for_output {pane_id, match, regex?, mode?, lines?, after_seq?, strip_ansi?, timeout_s?} blocks until one line of the pane's text contains match (or matches it when regex is true). It returns the pane.read result of the read that matched plus matched_line.
2. mode and lines work as in pane.read. In rendered mode only lines newer than after_seq count, and the cursor advances between polls, so a line already on screen never satisfies a wait started after it.
3. No match before timeout_s (default 3600) → TIMEOUT. An invalid regex → BAD_PARAMS. An unknown pane → NO_SUCH_PANE. A pane whose process has exited without a match → PANE_EXITED.
4. pane.clear {pane_id} blanks the screen and scrollback in every view: the server's grid and history, and attached clients, which receive the clear in the normal output stream with consistent offsets.
5. Both are in docs/08, method::ALL, the CLI (pane wait-output, pane clear) and integration tests.

Scope and clarification

Matching is per line, like herdr. herdr re-reads its whole window each poll, so an old matching line satisfies a new wait; rendered mode with after_seq avoids that, and screen/tail keep herdr's behavior. A clear that lands while the program is mid-escape-sequence can cut that sequence; terminals recover on the next byte. No unresolved requirements remain.