docs(framework/tools): lead TOOLS.md with high-salience fleet-tools cheatsheet

Agents (esp. Pi/Codex) under-use the buried tools index and hand-roll raw
`tmux send-keys` / raw `tea`/`gh` instead of the wrappers. Lead the doc with a
~25-line actionable block — #1 inter-agent messaging via tools/tmux/agent-send.sh,
#2 git wrappers + the GITEA_LOGIN auto-pick-by-origin-host rule (the
GetUserByName-on-USC trap) — and add the missing tmux row to the suites table.
Content-only; injected into every runtime prompt via buildRuntimePrompt.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QoYiBeKNh3BiYtAJS5Z587

packages/mosaic/framework/defaults/TOOLS.md

@@ -5,10 +5,39 @@ Tool suites live at `~/.config/mosaic/tools/<suite>/`. This is the index only.
 read it (or the relevant service guide) when your task actually touches that service.
 Project-specific tooling belongs in the project's `AGENTS.md`, not here.
 
+## ⚡ Most-used fleet tools (reach for these FIRST — don't hand-roll)
+
+You are a Mosaic fleet agent. These cover the highest-frequency cross-agent and git-provider
+tasks — use them before improvising with raw `tmux send-keys`, raw `tea`/`gh`/`glab`, or `curl`.
+
+**1. Message another agent** → `tools/tmux/agent-send.sh` (NOT raw `tmux send-keys`):
+
+```bash
+tools/tmux/agent-send.sh -s <target-session> -m "message"   # or -f <file> to send a file's contents
+```
+
+The coordinator session is `mos-claude` — send status, findings, and questions there.
+
+**2. Issues / PRs / milestones** → `tools/git/*.sh` wrappers (before raw `tea`/`gh`/`glab`):
+
+```bash
+tools/git/pr-create.sh ...   tools/git/issue-create.sh ...   tools/git/pr-merge.sh ...
+tools/git/ci-queue-wait.sh --purpose push|merge   # REQUIRED before any push/merge
+```
+
+**GITEA_LOGIN gotcha** — the wrappers default to login `mosaicstack`; on a USC repo that fails with
+`gitea / Error: GetUserByName ... not found`. Pick the login from the repo's `origin` host first:
+
+| origin host           | login                                    |
+| --------------------- | ---------------------------------------- |
+| `git.uscllc.com`      | `export GITEA_LOGIN=usc`                 |
+| `git.mosaicstack.dev` | default `mosaicstack` (no export needed) |
+
 ## Suites (use wrappers first)
 
 | Suite      | Path                                             | Purpose                                                                  |
 | ---------- | ------------------------------------------------ | ------------------------------------------------------------------------ |
+| tmux       | `tools/tmux/agent-send.sh`                       | inter-agent messaging (see "Most-used" above)                            |
 | git        | `tools/git/*.sh`                                 | issues, PRs, milestones, CI queue guard (platform-auto-detected)         |
 | woodpecker | `tools/woodpecker/*.sh`                          | CI pipelines (`-a mosaic`\|`usc`; match git remote host)                 |
 | portainer  | `tools/portainer/*.sh`                           | Docker Swarm stacks (status/redeploy/list)                               |