Add hosted agent metering upload path

[JaeLeex]

Summary

• Implements the agent-cli runtime slice from the hosted metering plan: hosted identity tagging, MCP-safe trade flags, ledger join fields, cache/route metadata, funded BTCSWP validation script, and hosted metering upload sidecar.
• Keeps agent-cli as runtime-only: no hosted subscription gating or gateway policy is added here.
• Emits the cost/runtime/trade data web-auth needs to meter per user/account/agent/plan/subscription.

Product framing

• This PR is for Hosted Runtime metering only. Basic BYO MCP Access stays free/included and does not require these env vars.
• Gateway quota PRs mcp-gateway Production Safety + Senpi Parity + Multi-Wallet (Phases 2.5–5a) #7/feat: add Venice as LLM provider #8 were closed; hosted quota enforcement lives in web-auth/provisioner/runner, not generic MCP gateway traffic.

Verified

• python3 -m pytest tests/test_cost_metering.py tests/test_metering_upload.py tests/test_mcp_money_tools.py tests/test_trade_command.py tests/test_pair_money_cli.py
• python3 -m py_compile scripts/metering_upload.py scripts/entrypoint.py scripts/pricing_aggregate.py

Docs

• Pricing architecture update: https://docs.google.com/document/d/1bnDI-Zfi9JulQipnEHvK5tvD1f4tMFwjT1IhvD_Nu28/edit
• Original cost experiment doc: https://docs.google.com/document/d/14QoyDzlWJji9q6TEzF38tjLOAbZUE6H6gC609QekCxs/edit

Remaining outside this PR

• Deployed hosted MCP smoke and real funded fills depend on the gateway/runner/web-auth deployment stack and funded wallet availability.

[JaeLeex]

Superseded by #60 (jl/hosted-metering-upload-20260701). Stack: #59 → #60.