Harness config 1.0.0-alpha.6

1.0.0-alpha.6 hardens the v1 manifest and projection contract for forward
compatibility, aligns the reference implementation with that contract, and
syncs the public English, Spanish, French, and Chinese specification content.

Manifest Compatibility

• Allows unknown top-level manifest fields and unknown fields on
  [[resources]], [[targets]], [[dir]], and [activation] as
  informational diagnostics instead of validation failures.
• Keeps singular [resources], [resources.<kind>], and [dir] tables
  invalid in v1.
• Adds harness.manifest_unknown_field so newer v1 manifests can be surfaced
  clearly to older tools.

Projection Semantics

• Defines idempotence over the managed projection subset M_n, so unmanaged
  target state and mutable-file edits do not contradict repeat activation.
• Clarifies that .harnessMutable is source-owned in v1 and does not read
  target-output .harnessMutable files.
• Requires .harnessProfile selectors to contain zero or one active profile;
  multi-profile selectors are now errors and do not participate.
• Documents deterministic override/profile precedence, target overlap
  rejection, shared first-segment override namespaces, and mutable resource
  composable outputs.

Docs And Tooling

• Updates Standard, Conformance, Tooling, Adoption, Diagnostics, and Testing
  docs with the hardened v1 behavior.
• Documents harnessc init --resource <kind> and --target <path>, removes
  stale plan command prose, and keeps website content links deploy-safe.
• Syncs the website-ready Spanish, French, and Chinese pages for the changed
  v1 semantics.