refactor!: remove legacy workspace importer (re-apply #1616)

[panghy]

Re-applies the legacy workspace importer removal by reverting the restoration commit 416663a (#1626). The content mirrors the original removal #1616 (squash 615f5dc), adjusted to current main.

HELD DRAFT — do not mark ready, do not merge. Parked until the feature is confirmed removable; tracking issue: intent-hq/intent#4082.

What's removed (same surface as #1616)

• Modules: crates/intentd/src/legacy_import.rs and crates/intentd/src/import.rs, including inline tests.
• CLI: the "intentd import" and "intentd import-legacy" subcommands.
• First-boot auto-import in serve (eligibility check, background task, import lock, shutdown abort).
• Wire surface: the system.importLegacy UDS fast-path RPC (trait method, SystemMethod::ImportLegacy, catalog entry, DaemonControl implementation).
• Tests: uds_legacy_import.rs, e2e_wss_legacy_import.rs, the importLegacy mock impls/cases, and INTENTD_LEGACY_IMPORT_ROOTS env stanzas.

Protocol — MUST be refreshed before merge

This is a pure revert-of-the-revert: it currently resets PROTOCOL_VERSION back to "9.0" and drops the 9.1 restoration history entry. Since 9.1 has been released (the restoration shipped), this removal is a second breaking change on top of it: when this PR eventually merges, the protocol must become 10.0. Before merge, redo:

• the PROTOCOL_VERSION constant (9.0 → 10.0),
• the version-history doc entries in protocol.rs (keep the 9.0 removal and 9.1 restoration records; add a 10.0 removal entry),
• the golden catalog counts against then-current main.

History

• Removal originally shipped in intentd 0.9.0 / cloudlands-fe alpha v2.123.0 (protocol 9.0, refactor!: remove legacy workspace importer #1616).
• Restored on main as protocol 9.1 (feat: restore legacy workspace importer (revert #1616) #1626).

Merge order for the removal: cloudlands-fe → intentd → monorepo docs.