fix: unify SCM audience and echo routing

[baixiaohang]

Summary

• centralize SCM audience composition around exact (humanAgentId, wakeAgentId) personnel authority while preserving distinct existing and legacy routes
• carry discriminated target-chat intent through GitHub persistence so strict personnel lines cannot fall back to another delegate's human-scoped mapping
• keep actor-echo cards in chat while suppressing only matching-line wakes, and move GitHub App Task data behind an opaque provider-task context
• update GitHub/GitLab parity coverage and the reusable cross-surface QA case

Validation

• targeted SCM, provider-adapter parity, target-chat, echo, and App Task suites (including an 8-file / 210-test pass and final adapter-specific reruns)
• pnpm exec vitest run --maxWorkers=2 --reporter=dot in packages/server (257 files, 2923 tests)
• pnpm typecheck (11/11 tasks)
• pnpm check (passes with 16 existing warnings and 1 info)
• git diff --check

Formal cross-surface QA is warranted for production webhook delivery, but was not started as part of this implementation task.

Scope

• no generic message.ts behavior changes
• no schema or migration changes
• no lifecycle, delivery-claim, cleanup, or orphan-chat reliability changes
• no merge requested; Context Tree reconciliation is required before merge because the GitHub routing node is decision-locked

[yuezengwu]

Implementation goal and core changes: this PR centralizes SCM audience composition around the exact (humanAgentId, wakeAgentId) pair, preserves distinct existing/legacy routes, carries strict personnel target-chat intent through GitHub persistence, keeps provider-task capability data discriminated, and changes actor echo handling so cards remain in chat while only the matching line's wake is suppressed. The core implementation is coherent, and I did not find a code-level defect in the reviewed diff.

Blocking governance issue: the current decision-locked Context Tree contract has not been reconciled with these behavior changes. system/cloud/automation/github-webhook-routing.md still says actor-owned entries are pruned before delivery and a self-only chat receives no card (S7/S11), while this PR deliberately writes a silent card. Its S2 target wording also still describes human-scoped existing-line reuse, while this PR moves authority to the exact human/wake pair and creates a strict current-delegate line when only a same-human/different-wake carrier line exists. decisionLocksCode: true means the existing Tree contract wins until the owners approve a replacement.

Please land the companion Context Tree reconciliation (and ensure both the GitHub-specific and provider-neutral SCM nodes state the same settled contract), then re-request review. There are no schema or migration changes, but the core in-memory routing data structures and delivery semantics changed, so this needs explicit human-owner inspection before merge.

I did not run tests per review scope. The current Test Server CI failure is a Docker pull failure, not a product-test failure.