feat: add /handoff /inbox /ack as dedicated top-level slash commands

Three thin alias skills that pass arguments straight through to the
underlying session-absorb subcommands. They give users single-word
slash commands instead of having to remember /absorb pass-through
syntax.

- /handoff [args]        runs session-absorb handoff
- /inbox [args]          runs session-absorb inbox
- /ack <id> [--note]     runs session-absorb ack

Each skill is ~30 lines: frontmatter (name, description, argument-hint)
plus a short routing block and quick examples. Descriptions are
scoped to "Use when the user types /<name>" so they don't auto-fire
on unrelated mentions.

Wired into command_install so future installs pick them up alongside
the existing /absorb alias. Onboarding footer updated to list the
new slash commands.

Author: ThatGuyAstro

skills/claude/ack/SKILL.md

@@ -0,0 +1,31 @@
+---
+name: ack
+description: Use when the user types /ack with a handoff id. Pass-through alias for `session-absorb ack` - marks a pending handoff as absorbed and records the acknowledgment timestamp and session id.
+argument-hint: "<handoff-id> [--note TEXT]"
+---
+
+# Ack
+
+Thin alias for `session-absorb ack`. Marks a handoff as absorbed.
+
+## Routing
+
+Pass arguments straight through:
+
+```bash
+$HOME/.local/bin/session-absorb ack {{ARGUMENTS}}
+```
+
+Task: {{ARGUMENTS}}
+
+## Quick examples
+
+```bash
+# Acknowledge handoff #3
+/ack 3
+
+# Acknowledge with a note back to the source
+/ack 3 --note "picked it up, continuing now"
+```
+
+To see what's pending in your inbox first, use `/inbox`.

skills/claude/handoff/SKILL.md

@@ -0,0 +1,36 @@
+---
+name: handoff
+description: Use when the user types /handoff. Pass-through alias for `session-absorb handoff` - writes a structured handoff brief (with optional --done / --pending / --blocked notes), logs it to the inbox, and optionally launches the receiving session.
+argument-hint: "[--target-cli claude|codex] [--done TEXT] [--pending TEXT] [--blocked TEXT] [--require-ack] [--no-launch] [...]"
+---
+
+# Handoff
+
+Thin alias for `session-absorb handoff`. Same behavior, shorter to type.
+
+## Routing
+
+Pass arguments straight through:
+
+```bash
+$HOME/.local/bin/session-absorb handoff {{ARGUMENTS}}
+```
+
+Task: {{ARGUMENTS}}
+
+## Quick examples
+
+```bash
+# End-of-day async handoff to whoever opens this cwd next
+/handoff --no-launch --target-cwd "$(pwd)" --done "API routes done" --pending "frontend wiring" --blocked "Stripe key"
+
+# Cross-CLI handoff with explicit ack required
+/handoff --target-cli claude --require-ack --done "refactor complete"
+
+# Same-CLI structured handoff that opens a fork
+/handoff --done "schema migrated" --pending "backfill job"
+```
+
+For the full flag list, run `session-absorb handoff --help` or see `~/.claude/skills/session-absorb/SKILL.md` and the project docs.
+
+For a click-driven flow that picks the source session for you, use `/absorb` and choose 🎯 More then 📦 Handoff.

skills/claude/inbox/SKILL.md

@@ -0,0 +1,39 @@
+---
+name: inbox
+description: Use when the user types /inbox. Pass-through alias for `session-absorb inbox` - lists pending handoffs targeted at the current session, cwd, or CLI. Defaults to the current context via CLAUDE_CODE_SESSION_ID and $PWD.
+argument-hint: "[--source claude|codex|all] [--cwd PATH] [--show-all] [--json] [--limit N]"
+---
+
+# Inbox
+
+Thin alias for `session-absorb inbox`. Shows pending handoffs targeted at you.
+
+## Routing
+
+Pass arguments straight through:
+
+```bash
+$HOME/.local/bin/session-absorb inbox {{ARGUMENTS}}
+```
+
+Task: {{ARGUMENTS}}
+
+## Quick examples
+
+```bash
+# Pending handoffs for this session / cwd / CLI
+/inbox
+
+# Include already-acknowledged ones
+/inbox --show-all
+
+# Machine-readable
+/inbox --json
+
+# Filter by another cwd
+/inbox --cwd ~/proj/api
+```
+
+Match rules: a handoff appears in your inbox if its `target_cli`, `target_cwd` (prefix match against your `$PWD`), and `target_session_id` are either null or match your current context.
+
+To acknowledge one, use `/ack <handoff-id>`.

skills/shared/session_absorb_core.py

@@ -3356,6 +3356,12 @@ def command_install(args: argparse.Namespace) -> int:
         results.append(
             install_skill_copy(claude_alias_source, CLAUDE_HOME / "skills" / "absorb")
         )
+    for alias_name in ("handoff", "inbox", "ack"):
+        alias_source = repo_root / "skills" / "claude" / alias_name
+        if alias_source.exists():
+            results.append(
+                install_skill_copy(alias_source, CLAUDE_HOME / "skills" / alias_name)
+            )
     print("\n".join(results))
     print()
     print("--- Onboarding ---")
@@ -3372,8 +3378,11 @@ def command_install(args: argparse.Namespace) -> int:
     print("    !sa fork-myself                # fork the CURRENT session into new Terminal")
     print("    !sa list --active-only         # list active sessions")
     print()
-    print("  For a clickable in-chat picker (slow but conversational):")
-    print("    /absorb")
+    print("  Slash commands available in Claude Code:")
+    print("    /absorb       # click picker, default daily flow")
+    print("    /handoff      # write a structured handoff (with --done / --pending / --blocked)")
+    print("    /inbox        # see pending handoffs targeted at this session / cwd / CLI")
+    print("    /ack <id>     # acknowledge a handoff so the source knows it landed")
     print()
     print("Full reference: see docs/reference.md or run `session-absorb --help`.")
     return 0