docs(rfd): Add RFDs 074–080 and clarify draft superseding in RFD 001

[JeanMertz]

Add seven new RFDs covering the next wave of design work:

• RFD 074 (Discussion): Eager loading with command-declared data requirements. Replaces lazy OnceLock loading with a two-phase startup pipeline where commands declare filter_needs and target_needs upfront, enabling infallible data access at runtime.

• RFD 075 (Discussion): Tool sandbox and access policy. OS-level sandboxing for subprocess tools via sandbox-exec on macOS, Landlock on Linux, and restricted tokens/job objects on Windows. Extends RFD 076's AccessPolicy with CommandRule for spawn restrictions.

• RFD 076 (Accepted): Tool access grants. Typed access field on tool config declaring filesystem, network, and environment-variable grants. Tools self-enforce via ctx.check_*() helpers; OS-level enforcement is RFD 075's responsibility.

• RFD 077 (Discussion): Plugin configuration and trust policy. Introduces a [plugins] section in AppConfig with per-plugin install policy, execution policy, checksum pinning, and opaque options. Replaces standalone approval files.

• RFD 078 (Accepted): Tool config mutation. Adds access.config as a fourth resource type in RFD 076's access model. Tools declare config read/write grants, return outcome.config / outcome.unset, and rejected deltas trigger re-invocation with context.delta_rejection. Approved deltas accumulate in a per-cycle commit buffer and are emitted as a single ConfigDelta at cycle end.

• RFD 080 (Discussion): Editor as a config source. Moves editor invocation from Query::run into the startup pipeline so the editor's TOML preamble is resolved as a proper config layer before Ctx is constructed, eliminating the phantom-delta bug and making editor-provided values visible to the current turn.

Also updates RFD 001 to clarify that drafts cannot be superseded — a draft replaced before promotion is deleted, not superseded. Supersedes relationships only apply from the Accepted state onward.