refactor: complete architecture cleanup

[zatevakhin]

Phase 11 architecture cleanup

This publishes the independently approved Phase 11 aggregate as one review PR:

• 2c4daf2: remove App migration forwarding helpers and the duplicate reconciler.
• 97e9e55: remove temporary test exports/aliases and cross-module wildcard imports.
• 2e8a28d: remove the crate-wide dead-code blanket and compiler-identified dead surfaces while narrowing visibility.
• 5761124: add the architecture checker and 20 self-tests, and enforce architecture plus all-feature Rust commands in CI.
• 8005080: document the module map, event/effect and ACP flow, boundaries, exceptions, and testing in README.
• e1b308b: reject nested and combined crate dead-code allowance bypasses.
• 54a6c919: scan every same-line crate inner attribute.

Approved range: 520870a57b0ce3b0983e6af1ed5f632c0b78e27e..54a6c9194ffb17b10a3052485fd226e93503a5f2 (42 files, +1248/-697). Independent Linus review approved the cleanup through 2e8a28d, then approved the final corrected aggregate with no findings.

Validation on exact head

• Architecture checker: 20/20 self-tests; repository scan passes all 145 Rust files.
• Python/YAML: checker py_compile passes without residue; all five CI YAML files parse.
• Rust: formatting, check, Clippy with -D warnings, and build pass for all targets/features.
• Tests: two debug and two release all-target/all-feature runs each pass 1,159/1,159 with 0 failed and 0 ignored; inventory is 1,159 tests and 0 benchmarks.
• Focused suites pass: diagnostics 15, application 62, runtime 182, handlers 49, ACP state 87, mesh 50, UI 124, App 39, ACP contracts 13, and features 170.

Compatibility retained includes the supported delegate_models migration, hidden --acp-websocket, twelve pub(crate) App fields, generated-theme allowance, item DTO allowances, and cfg(test) render adapters. Protected paths, Cargo manifests/lockfile, and generated themes are unchanged.

Environmental validation remains intentionally unclaimed for live ACP/backend, external WebSocket, subprocess stdio, terminal, clipboard, interactive UI, and the Phase 0 performance baseline. Knowledge query/ingest is unavailable because of a provider database schema error and is not a source-validation blocker.

This PR is ready for user review. It is intentionally left open and must not be merged yet.

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