v0.8.1 — MCP add_task fallback, doctor sees shadowed .mcp.json

A dogfooding finding: /sf:change dead-ended on a missing MCP tool it never needed. An agent running /sf:change had to add a task for a net-new FR, found no add_task in the MCP surface, found no add-task in bin/task-master either, and handed the work back to the user as "tooling unavailable". Two separate defects made that dead end reachable.

The command docs pointed at exactly one way to add a task, and it was the fragile one. commands/change.md step 4 named mcp__task-master-ai__add_task with no alternative, and commands/phase.md's Task Master note scoped its CLI fallback to a single trigger — "if any MCP TM call errors with a missing API key" — which does not cover a tool that is simply absent from the surface. Meanwhile the deterministic twin had shipped with the native engine all along: flow-tools.cjs task-add / task-get / task-list / task-set-status / task-next write the same .taskmaster/tasks/tasks.json with no AI and no MCP, and none of them were documented anywhere. The agent's conclusion was correct given what it could read. commands/phase.md now carries the full MCP-op to engine-CLI mapping table and a fallback that fires on an absent tool as well as a provider error; change.md and resync.md inline the two ops they actually need; the README documents all five commands.

/sf:doctor could not see the actual cause: a project-level .mcp.json shadowing the bundled server. The target project still had its own mcpServers["task-master-ai"] entry (npx task-master-ai, TASK_MASTER_TOOLS=core) left over from a pre-cutover task-master init. That entry wins over the plugin's manifest, so the session was talking to a legacy core-tier server whose 7-tool surface has no add_task. The existing dep-lock check reads .mcp.json at the plugin root only, so it reported "native task engine bound" while the live binding was legacy. New mcp-shadow check reads .mcp.json in the project cwd and warns when a task-master-ai entry there is not the native binding, naming the tier and the two fixes; skipped when cwd is the plugin root.

782 Node tests green (2 new).