Skillscript

Closes Perry's two requirements on the AgentConnector contract before
substrate-author wires their adopter-side impl. The verbs were already
well-generalized (his endorsement: list_agents / deliver / wake
maps cleanly across Slack / Discord / tmux / webhook / email / queue —
nothing substrate-specific leaks in). v0.18.2 bakes in the two robustness
properties that keep the contract substrate-neutral as adoption grows.

A. WakeReceipt.woken: boolean — explicit honesty signal

New required field on the wake receipt. Wake-capable substrates set
woken: true; passive substrates that can't interrupt (webhook,
file-drop, store-only) degrade gracefully — return woken: false
instead of throwing. Per Perry's degradation requirement: "conform by
degrading, never by erroring."

Callers reading the receipt distinguish interrupted-them from
delivered-only without per-substrate knowledge. The pattern mirrors
DeliveryReceipt.delivery_skipped (v0.9.6 — adopter signals
accepted-but-not-pushed).

NoOpAgentConnector.wake() now returns {woken: false, ...} (it
can't actually interrupt anything).

HttpWebhookAgentConnector example: when no wake_url configured for
an agent, returns {woken: false} instead of throwing. Real HTTP
failures (POST to configured wake_url returns 4xx/5xx) still throw —
distinct from the substrate-capability case.

B. Session-granular targeting — agent@session composite

agent_id parameter on deliver and wake now documented as opaque
composite the substrate decomposes. Bare identifier (Slack @user,
email address) and composite (perry@kitchen-terminal,
alice@browser-tab-3) both supported — substrate parses if it tracks
sessions, ignores the suffix if it doesn't.

WakeOpts.session_id?: string — structured alternative for callers
with the session already separated (e.g., dashboard's per-session
"wake this terminal" action). Substrate impl chooses which signal to
honor when both are present.

DeliveryReceipt.session_id?: string — symmetric reflection: when
delivery routed to a specific session, the receipt names it.

Per Perry: "One-identity-many-live-sessions isn't an AMP quirk — it's
general (multiple terminals, multiple chat sessions). If the contract
only knows bare agents, it can't express the wake-class targeting we
just built."

Tests

8 new tests in v0.18.2-agent-contract-degradation.test.ts:

• WakeReceipt.woken honest across NoOp + HttpWebhook
• Caller misconfiguration still throws (distinct from
  substrate-can't-wake case)
• agent@session composite parsing through a CompositeAwareConnector
  test impl
• WakeOpts.session_id structured form wins over embedded suffix
• Bare agent_id (no @) still works

1690 tests total. Narrow-core LOC ceiling 10500 → 10600.

Contract diff for adopters writing impls

Existing impls compile but won't typecheck without the new required
WakeReceipt.woken field. Per the pre-adoption rule, this is a cheap
breaking change — the only known impl-in-flight (substrate-author's
AmpAgentConnector) is being written against this contract.