refactor: centralize native front-door runtime

[RNT56]

Summary

• replace three duplicated native runtime wiring blocks with one configureNativeRuntime seam
• cover run/watch/resume/swarm, terminal chat/TUI, and channel serve without changing their front-door-specific tools, inbox, emitter, ask, or wake behavior
• centralize advisor metering, repo orientation, proactive context compaction, live code intelligence, memory/lessons, and trusted steering
• add a constructor-level parity test over all three real builders, including default-off and opt-in live-index controls

Why

Recent audits repeatedly found capabilities that were implemented and tested in one path but inert on another. The duplicated composition blocks were the structural cause; this makes one shared configurator the only production assignment site for the cross-cutting native seams.

Verification

• constructor parity regression test
• GOTOOLCHAIN=go1.25.12 make verify
• GOTOOLCHAIN=go1.25.12 make test-race
• GOTOOLCHAIN=go1.25.12 make tui-verify
• pinned govulncheck v1.6.0: no vulnerabilities found
• pinned golangci-lint v2.12.2 with a fresh worktree-specific cache: 0 issues
• git diff --check