## Why

Platform can currently queue dependency and Run update jobs, but Run returns synthetic success without executing a declared install step or downloading, verifying, staging, activating, and recovering an update. Operators therefore see completion for work that did not happen, and the existing job/artifact security boundaries are not yet sufficient for real machine mutation.

## What Changes

- Resolve plugin-declared dependency probes and install plans through Platform ownership, installed-plugin, runtime-profile, binding, endpoint, platform, session, attempt, and lease checks.
- Expose a safe, reviewable dependency catalog and require approval of the exact immutable plan digest before dispatching an install.
- Execute only typed package, verified-download, and SteamCMD steps through fixed adapters; reject arbitrary shell, scripts, unsafe package arguments, unapproved downloads, undeclared targets, stale plans, and unsupported operating systems.
- Persist dependency execution status/evidence and project terminal job results into bounded, redacted Platform records and UI status.
- Add a Run-only, fenced, resumable artifact download contract for approved same-server Run distributions.
- Download, checksum-verify, safely extract, stage, and durably journal Run updates; activate them through a post-result helper, verify startup health, and roll back on activation failure.
- Persist Run update phases and audit outcomes without exposing host paths, Run/session/lease tokens, secret refs, credentials, PIDs, sockets, or private plan bindings.
- Preserve control/job/log/artifact channel isolation so dependency downloads and update transfer/activation do not delay heartbeat, job acknowledgement/result, cancellation polling, or log upload.

## Capabilities

### New Capabilities

- `durable-dependency-execution`: reviewable declared dependency plans, fenced Run input, typed probes/install adapters, persistence, recovery, cancellation, and safe projections.
- `transactional-run-self-update`: approved artifact download, resumable verification, durable staging, post-result activation, startup health confirmation, rollback, and audit semantics.

### Modified Capabilities

- `run-distribution-and-client-managers`: dependency and self-update jobs now perform real bounded machine work instead of success-only hooks.
- `artifact-transfer-channel`: authenticated Run jobs can read approved distribution artifacts in bounded resumable chunks without using browser download sessions.

## Impact

- Affects `plugins/` dependency declaration validation/SDK examples, `platform/` domain/DTO/model/repository/service/protocol/validator/API layers, projection-only `platform_web/` dependency/update status, and the independent `run/` protocol/runtime/config/shared layers.
- Adds no arbitrary shell capability and no raw host path, credential, socket, token, lease, session hash, or secret projection to plugins or platform_web.
- Does not implement client-manager lifecycle, dependency installation outside declared adapters, Run distribution signing infrastructure/KMS, production rollout rings/fleet orchestration, plugin lifecycle, production scaling/alerts, or real AI-provider integration.