Add injectable Netdata state bridge to Systems observability

[Mjones13]

The existing Systems observability flow has no source bridge from an explicitly supplied Netdata client to per-host refresh state. Add portable Systems/refresh models and an injectable observation bridge that publishes host state into the existing Systems and Overview views and environment-host mapping. The optional bridge is empty by default; it introduces no endpoint defaults, automatic requests, timers, watchers, settings schema or account-control activation.

This dependent PR targets #5 at 1849a8cb0a4235b4e406036cc65316e99f53c0ba; its parent chain remains #5 → #4 → #2. The cumulative fifteen-path diff includes the two completed source units and a bounded six-file correction of twenty inherited SwiftFormat diagnostics. Parent PR ownership remains unchanged. The formatting correction preserves whitespace-independent tokens except two equivalent private test-fixture syntax rewrites; it changes no runtime behavior, freshness, control, settings, architecture policy or workflow.

Validation:

• The source units at d64dfbef244aabcec43ebb1158ea1cb277aacc0d passed 42 synthetic tests across five suites and the required contained Linux make test with 75 discovered/selected selections in seven first-pass groups. These sets overlap and are not added together. They cover bridge rebinding, cancellation, stale results, physical single-fetch occupancy, portable state, observability and client regression.
• Corrective head ada1598a67642644ebb943d71c705950848ff0b9 preserves those behavioral inputs. All six corrected files passed CI-pinned SwiftFormat 0.61.1, strict SwiftLint 0.65.0, Swift 6.2 frontend syntax parsing and whitespace checks. The changed work note passed documentation-link checks. Unchanged behavior tests were not repeated for formatting.
• Verification used authenticated Swift 6.2 with a separately authenticated genuine Observation 6.2.2 runtime and contained Debian dependencies. Initial tool/link failures, final provenance, lock invariants, exact input hashes and scratch cleanup are recorded in the work notes.

The old head's hosted run 37065791842 attempt 1 ended in failure: changes, lint and all three Linux jobs passed; both macOS shards failed. Shard 0 stopped at the twenty inherited formatting diagnostics and skipped Swift Test. Shard 1 skipped formatting and failed the Italian localization catalog test with one issue; the exact assertion detail remains unavailable. The unchanged fixture alone does not establish the input-catalog cause. This formatter correction does not claim to fix that separate localization failure or make all CI pass. Current-head hosted checks remain to be observed on the existing macOS route.

Native Mac app constructor/typechecking/rendering, screenshots, installed client behavior, private endpoint access, live telemetry correctness and owner acceptance remain unproved. Existing parent CI and architecture gates remain applicable. NETDATA-CLIENT-01 P2 and NETDATA-DOC-01 P3 remain unchanged and undisposed; this change does not resolve the original client freshness finding.

Source records: portable state work note and bridge work note.

Contributing T3 contexts:

• Original client continuation: “Resume NetData Menu Bar Monitoring,” native thread 718b02d7-0d4b-4670-b05f-57a5db28178d.
• Portfolio source coordinator: “Orchestrated thread work stream processing,” /root, with sole source/Git lane /root/portfolio_slot_14. The current portfolio native thread ID is unavailable in the bound context and is not inferred from a worktree or goal identifier.

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