## Why

Issues #77 and #78 made `NenjimHub` the owner of runtime composition,
process startup, and immutable started-process snapshots, but the existing
Process Manager is still disconnected from that runtime. It is neither
Hub-managed nor backed by the Hub's truthful process IDs.

## What Changes

- Make `NenjimProcessManager` a specialized canonical `NenjimProcess`.
- Inject the owning `NenjimHub` into the reference Process Manager.
- Construct and register the Process Manager as
  `nenjim.process-manager.default`, then start it last through the Hub's
  ordinary process-start mechanism.
- Replace the hardcoded JavaFX rows with complete ordered snapshots of
  `NenjimComponentId.value()` strings from the Hub.
- Poll immediately and every three seconds on one daemon background worker,
  while publishing all JavaFX mutations through the existing runtime helper.
- Retain the last successful display after a polling failure and stop the
  worker cleanly when interrupted.

## Capabilities

### Added Capabilities

- `nenjim-process-manager`: define the Hub-managed Process Manager lifecycle,
  polling, JavaFX publication, failure handling, and displayed-ID semantics.

### Modified Capabilities

- `nenjim-component-registry`: extend Hub composition and successful startup
  order with the Process Manager while preserving the common lifecycle rule.

## Impact

Affected code is limited to the Process Manager contract and reference
implementation, the Hub composition root, and this active OpenSpec change.
Polling is a temporary observation mechanism; no events, controls, health
model, metadata, persistence, stop lifecycle, test framework, or deployment
change is introduced.