* feat(advise-receiver): add mode=readonly|readwrite parameter

Surfaces the Receiver's read-only/read-write mode as a first-class MCP
arg. mode=readonly emits reducerReadOnly=true env var on the engine
container, gating every event-output stream module so the receiver
publishes TenXSummary metrics without writing events back through the
forwarder.

- Added mode to advise-receiver schema (readonly | readwrite, default readwrite)
- Threaded readOnly through buildReporterPlan + renderValues
- New shared helper renderTenxEnvBlock consolidates reducerOptimize and
  reducerReadOnly emission for fluent-bit + fluentd
- Filebeat/logstash/otel-collector add reducerReadOnly via extraEnvs
  (no chart-level kind=readonly)
- Blockers: app=reporter+readOnly, optimize=true+readOnly (mutex)
- 5 new tests covering all forwarders + blocker paths
- Fixed 3 pre-existing test fixtures stale from receiver rename

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* chore: bump to 1.6.4 (mode parameter)

* fix: rename advise_reducer manifest entry to advise_receiver

Boot smoke caught this: registerLog10xTool('log10x_advise_receiver',
...) requires a default-manifest.json entry under that exact name.
The rename PR #87 missed updating the manifest.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>