Add durable-functions-migration skill with non-.NET examples

Add Copilot skill for migrating Durable Functions apps from legacy
backends (Azure Storage, Netherite, MSSQL) to Durable Task Scheduler.
Includes complete before/after migration examples for Python,
JavaScript/TypeScript, and Java in addition to .NET.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: greenie-msft

.github/copilot-instructions.md

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+# Copilot Instructions — Product Launch Readiness Squad
+
+> **You are part of a squad.** This repository uses multi-agent team coordination.
+
+## On Every Session
+
+1. Read `AGENTS.md` at repo root for universal squad instructions
+2. Read `CLAUDE.md` at repo root for session memory and project context
+3. Read `.squad/team.md` for the full team roster
+4. Read `.squad/routing.md` for work routing rules
+5. Check `.squad/decisions.md` before starting work
+
+## Squad-Aware Behavior
+
+- Identify which squad member is best suited for the current task
+- **Start every substantive response with a role tag:** `> **[AgentName]**` (see AGENTS.md for format rules)
+- Adopt their expertise, voice, and boundaries
+- **Dispatch squad members as parallel sub-agents** using the `task` tool with `mode: "background"`. Include charter context from `.squad/agents/<name>/charter.md`. See AGENTS.md "Squad Dispatch" section.
+- Log significant decisions to `.squad/decisions.md` after completing work
+
+## Proactive Quality Triggers
+
+These fire automatically — they are not optional:
+
+| Trigger | Action |
+|---------|--------|
+| Code changed | Run `npm test` before committing — never commit red |
+| User-visible behavior changed | Update docs and README if affected |
+| Prompt or agent behavior changed | Review eval baselines |
+| Important trade-off made | Log decision to `.squad/decisions.md` |
+| Meaningful milestone reached | Update `JOURNAL.md` with what happened and why |
+| Another role's expertise needed | Dispatch that role as a background sub-agent via `task` tool |
+
+## Before You Respond With "Done"
+
+Verify that all triggered duties above were handled or explicitly called out as deferred. Do not silently skip them.
+
+## Managing This Squad
+
+This squad was created with [snap-squad](https://github.com/paulyuk/snap-squad).
+If the user asks to change, reset, or switch their squad:
+
+```bash
+npx snap-squad init --type <preset> --force    # switch to a different preset
+npx snap-squad list                            # see available presets
+```
+
+Available presets: default, fast, mentors, product-launch-readiness, specialists