install: write a single HTTP client entry when daemon mode is opted into #412

Part of #408. Depends on daemon lifecycle.

Why

synthesizeMcpEntry() (bin/install-helpers.cjs) emits a stdio entry per provider. Daemon mode needs a single HTTP client entry instead.

What

When daemon mode is opted into, install writes one entry of the form:

{ "type": "http", "url": "http://127.0.0.1:<port>/mcp" }

instead of per-provider stdio entries.

Opt-in, not default. Consolidation changes tool names (mcp__claude-1__claude becomes mcp__unified-1__claude-1), which is breaking for anything referencing the old names. Landing that silently on ~1.2k downloads/month is not acceptable; default can flip in a later milestone once the path is proven.

Reuse findUnifiedMcpEntry() from #408's first fix so a user who already consolidated is recognised rather than re-slotted.

Acceptance

• opt-in flag writes exactly one HTTP entry
• absent the flag, behaviour is unchanged for existing users
• quorum tool_prefix values resolve correctly under the HTTP entry (see unifiedToolPrefix)