fix(tabs): only mention read_tab when the sender actually has it; CAPS on ONLY

The send_to_tab guidance previously told the agent it could call read_tab to
check for a reply, but the tab-messaging permissions are split — a tab can
hold send_to_tab WITHOUT read_tab (the exact case in testing). Advertising a
tool the agent wasn't granted is wrong.

Thread a canReadTab flag from AgentManager.buildTabCommToolEntries into
createSendToTabTool (true iff this tab is also granted read_tab). The tool
description and the delivery-result text now only reference read_tab when
canReadTab is true; otherwise they say a reply arrives on its own and to end
the turn. Drop the read_tab phrasing from the static TOOL_DESCRIPTIONS
one-liner (can't be conditional per-tab there).

Also uppercase ONLY in the recipient reply-contract footer for emphasis.

Tests: cover both canReadTab branches for description + result text; assert
ONLY is uppercased.

0 files changed, 0 insertions, 0 deletions