feat: bidirectional upstream sync + auto-propagation for tiered squads

Problem

The current squad upstream command is one-way pull-only with no auto-sync. This creates two gaps for tiered squad deployments:

1. No bidirectional flow (child → parent)

A child squad that discovers something useful (a skill, a decision, a governance improvement) has no way to propose it back to the parent squad. The only flow is parent → child via squad upstream sync.

2. No automatic propagation (parent → child)

When the parent squad changes (new governance rules, updated templates, new skills), child squads see nothing until someone manually runs squad upstream sync. There's no webhook, no watcher, no GitHub Action that triggers child updates.

Current State

squad upstream today supports:

�dd — register a parent squad (git URL, local path, or export JSON)

emove — unregister

list — show configured upstreams
sync [name] — pull latest from parent (git pull or validate local path)

All operations are read-only from the parent. The child caches the parent in .squad/_upstream_repos/.

Proposed Enhancements

Phase 1: Auto-sync (parent → child)

squad upstream watch — poll parent repo for changes on an interval (like Ralph's watch)
GitHub Action — squad-upstream-sync.yml that runs on a cron and syncs from parent, opening a PR if there are changes
Selective merge — config to specify which parent files to adopt vs override locally (e.g., adopt templates but keep local routing)

Phase 2: Bidirectional (child → parent)

squad upstream propose — packages a child's changes (new skills, decisions, governance tweaks) and creates a PR on the parent repo
Scope control — config to specify what the child is allowed to propose (skills only, decisions only, everything)
Conflict resolution — when parent and child both changed the same file, present a merge UI or default to parent-wins

Phase 3: Event-driven sync

Webhook-based — parent repo sends a webhook on push, child auto-syncs (no polling needed)
GitHub Actions integration — parent's CI triggers child repo dispatch event via
epository_dispatch

Feature: Tiered Squad Deployment — Hub Repos, Companion Repos, and Meta-Hub for Clean Production Repos #242 — Tiered Squad Deployment (broader vision, this issue implements one piece)
Design: Cross-Squad Orchestration — coordinating work across multiple Squad instances #316 — Cross-Squad Orchestration (complements this — focuses on runtime coordination, this focuses on config/state sync)

This issue is scoped specifically to the \squad upstream\ command and its gaps. Not a duplicate of #242 — it's an implementation plan for one capability within that vision.

🏗️ Squad Triage — Flight (Lead)

Issue: #357 — feat: bidirectional upstream sync + auto-propagation for tiered squads
Assigned to: FIDO (Quality Owner)
Reason: Issue relates to testing/quality work

@copilot evaluation: 🔴 Not suitable — issue involves work outside the coding agent's capability profile.

Team roster:

Flight (Lead) → label: squad:flight
Procedures (Prompt Engineer) → label: squad:procedures
EECOM (Core Dev) → label: squad:eecom
FIDO (Quality Owner) → label: squad:fido
PAO (DevRel) → label: squad:pao
CAPCOM (SDK Expert) → label: squad:capcom
CONTROL (TypeScript Engineer) → label: squad:control
Surgeon (Release Manager) → label: squad:surgeon
Booster (CI/CD Engineer) → label: squad:booster
GNC (Node.js Runtime) → label: squad:gnc
Network (Distribution) → label: squad:network
RETRO (Security) → label: squad:retro
INCO (CLI UX & Visual Design) → label: squad:inco
GUIDO (VS Code Extension) → label: squad:guido
Telemetry (Aspire & Observability) → label: squad:telemetry
VOX (REPL & Interactive Shell) → label: squad:vox
DSKY (TUI Engineer) → label: squad:dsky
Sims (E2E Test Engineer) → label: squad:sims
Handbook (SDK Usability) → label: squad:handbook
Ralph (Work Monitor) → label: squad:ralph
@copilot (Coding Agent) → label: squad:copilot

To reassign, remove the current squad:* label and add the correct one.

📋 Assigned to Flight (Lead)

Issue: #357 — feat: bidirectional upstream sync + auto-propagation for tiered squads

Flight will pick this up in the next Copilot session.

For Copilot coding agent: If enabled, this issue will be worked automatically.
Otherwise, start a Copilot session and say:
Flight, work on issue #357