feat(installer): bootstrap a managed local PowerContext runtime #2115

Goal

Prepare a verified, isolated local PowerContext runtime from Desktop on Windows 11 x64 and macOS Apple Silicon/Intel without requiring preinstalled Python, uv, Git, or compilers. Network installation of pinned compatible resources is the first-wave delivery.

Parent: #2114. First-wave release: #2099. Linux #2110 / #2111 is optional and does not block this issue.

PR breakdown

• PR 10-A — Installation resources, plans and recovery contract. Define supported resource/version identities, ownership records, non-mutating preflight, approved plan identity, paths, locks, operation status, cancellation boundaries and interruption recovery. Define how existing installations, occupied ports, unsupported database versions and environment damage are reported.
• PR 10-B — Bootstrap, install and repair. Obtain and verify compatible resources, prepare the managed runtime, invoke supported configuration/service operations and persist per-component results. Implement repeat-run recovery and repair for owned installations without overwriting user-managed environments or data.

Dependencies and coordination

• build(desktop): publish Desktop and local runtime installation artifacts #2112 owns building/publishing versioned installation resources and their trusted identity; this issue owns obtaining and installing them on user machines. Agree on the manifest/resource interface early.
• feat(ops): expose structured personal Server lifecycle operations #2116 owns service/configuration operation boundaries and lifecycle rules; share plans, locks and durable status rather than running an independent competing installation controller.
• feat(desktop): guide local Server setup and lifecycle management #2117 consumes structured progress and results; feat(desktop): integrate Server discovery and operation compatibility #2101 consumes actual runtime identity and qualified compatibility.
• build(desktop): deliver signed Windows preview packages #2108 / build(desktop): qualify signed and notarized macOS packages #2109 integrate the bootstrap entry/helper into distributable packages and qualify Windows/macOS. No dependency on Linux acceptance.
• Follow RFC docs(rfc): define usability and agent workflows #1733. Tracking Issue: manifest-driven installation outside the runtime CLI #1406 is a retired plan, not a prerequisite or evidence that an installer already exists. Preserve current service and configuration invariants where implementations are reused.

Acceptance criteria

• The installation entry starts on a clean supported machine without a system Python. A managed Python runtime may run the Server after bootstrap; Windows includes the required pythonw.exe.
• Sources, platform/architecture, exact versions, checksums and trust decisions are native/producer-owned. Untrusted renderer URLs or a checksum supplied beside an untrusted download cannot authorize execution.
• Runtime dependencies are resolved from verified compatible distribution resources; users do not compile dependencies or clone repositories. Existing PATH/tools are not silently replaced.
• Programs, protected configuration and user data have separate locations/ownership. First use defaults to SQLite/user data and model-free basic operations, following the local policy in Tracking: deliver personal local Server setup and management in Desktop #2114.
• Preflight distinguishes owned/current, missing, repairable, foreign/unknown, occupied-port and incompatible states. Apply revalidates the approved target and cannot silently take over an existing service.
• Repeated installation, interrupted download, integrity failure, partial setup and Desktop exit preserve prior results and expose a supported resume/repair action; secrets never enter progress/journals.
• Configuration, service registration, service readiness and usable connection are separate outcomes. Return actual endpoint/installation identity and supported secure credential references rather than guessed defaults.
• Repair preserves user data and configuration choices. An incompatible existing database requires supported migration/maintenance; do not delete it or run an incompatible old runtime.
• Clean Windows/macOS acceptance uses the published resource identities; failures are actionable and work is not credited from fixtures alone.

Non-goals

Automatic Agent setup, arbitrary source builds, global Python modification, automatic version upgrades, arbitrary database migration/rollback, complete offline distribution, and first-wave Linux delivery.