[Epic] oc-plugins v1.0.0 roadmap

# oc-plugins v1.0.0 Epic

`oc-plugins` is a Rust CLI for managing configured npm-based OpenCode plugins.

## Active v1 scope
- OpenCode-only
- npm-based plugins only
- configured-plugins-only inventory
- calm, premium human output
- stable `--json` for scripts
- safe config mutations with preview/dry-run/confirmation

## Active milestone chain
| Milestone | Issue | Status |
| --- | --- | --- |
| M1 Foundations | #33 | Closed |
| M2 Read Path | #32 | Closed |
| M3 Registry Enrichment | #35 | Closed |
| M4 Safe Mutations | #36 | Closed |
| M5 Polish | #34 | Closed |

## Child issues
- #33 foundations work: scaffold, config providers, extraction, output model, error model
- #32 read path work: list, curated catalog, cache, manifest resolution
- #35 registry enrichment: npm lookups, outdated, startup cache writes, self-update detection
- #36 safe mutations: add, remove, update with dry-run, preview, and confirmation
- #34 polish: rendering refinements, output guarantees, and speed validation

## Deferred future ideas
- #41 diagnostics: revisit a safer `oc-plugins doctor` experience outside the active v1 milestone chain

## Current status
- The active v1.0.0 milestone chain is complete.
- Rust is the chosen implementation stack for v1.0.0.
- Deferred ideas should stay visible, but not distort active milestone definitions.
- Next work is release/PR preparation and publication workflow decisions.