feat(rules): add triggers.md for cross-project launch phrases

Adds claude-rules/triggers.md as the home for phrases the user says from any cwd to invoke a cross-project action. First entry: "launch project X" → run the ai script in single-project mode targeting the matched basename. Ambiguity handling: list candidates and ask rather than guess.

The trigger phrases already in protocols.org ("Let's run the [X] workflow", "Wrap it up") are project-scoped. They assume an active .ai/ session. Cross-project launchers don't fit that layer; they need to work from any cwd, including outside any project. None of the existing claude-rules files (commits.md, testing.md, verification.md, subagents.md, interaction.md, cross-project.md, todo-format.md) had a clean fit either. A new file is the smallest architectural change.

Makefile picks up new claude-rules/*.md files via wildcard, so no Makefile change needed. make install created the symlink at ~/.claude/rules/triggers.md; make doctor reports 39/0/0.

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+# Cross-Project Trigger Phrases
+
+Applies to: `**/*`
+
+Trigger phrases the user can say from any session to invoke a cross-project action. These live in the global rules layer because they cross project boundaries — the user can be sitting in any cwd, including outside a project, and the phrase still means the same thing.
+
+## "Launch project X"
+
+Synonyms: "Launch X", "Open project X", "Switch to project X".
+
+**Action:** run the `ai` script (the Claude Code session launcher, installed at `~/.local/bin/ai`) in single-project mode targeting the named project.
+
+```
+ai <project-path>
+```
+
+The `ai` script handles tmux session creation, window placement, and the per-project Claude opening line — see `~/code/rulesets/claude-templates/bin/ai` for the canonical source.
+
+**Resolving X.** Match against project basenames discoverable by `ai` — directories under `~/code/`, `~/projects/`, and `~/.emacs.d` that contain `.ai/protocols.org`.
+
+- Exact basename match (case-insensitive) → invoke `ai <path>` directly.
+- No match → list all available basenames, ask which to launch.
+- Multiple partial matches (X is a substring of two or more candidates) → list the matching basenames, ask which.
+
+Do not guess. The cost of asking once is one short turn; launching the wrong project is a wrong-context Claude session that has to be killed and restarted.
+
+## Why a separate file
+
+Other claude-rules files cover specific concerns: `commits.md` for the publish flow, `subagents.md` for delegation, `testing.md` for test discipline. None is a natural home for "phrases the user says to trigger global actions." The trigger phrases in `protocols.org` (`Let's run the [X] workflow`, `Wrap it up`) are project-scoped — they assume an active `.ai/` session. Cross-project launchers warrant their own file.
+
+## Adding new triggers
+
+Same shape. Each entry: phrase (in quotes), synonyms, the action, ambiguity handling.