cli: unify datamachine agent / agents — one noun, one class

[chubes4]

Closes #1172.

Summary

Realigns datamachine agent / datamachine agents with the project's singular/plural aliasing convention. Every other DM noun (flow/flows, pipeline/pipelines, post/posts, handler/handlers, job/jobs, block/blocks, step-type/step-types, processed-item/processed-items, setting/settings, log/logs, link/links) routes both forms to the same class. agent was the lone outlier, routing to MemoryCommand instead of the AgentsCommand that agents routes to.

Change

One-line swap in inc/Cli/Bootstrap.php:

-WP_CLI::add_command( 'datamachine agent', Commands\MemoryCommand::class );
+WP_CLI::add_command( 'datamachine agent', Commands\AgentsCommand::class );
 WP_CLI::add_command( 'datamachine agents', Commands\AgentsCommand::class );

-// Backwards-compatible alias: `wp datamachine memory` → agent.
+// Canonical home for agent memory-file operations.
 WP_CLI::add_command( 'datamachine memory', Commands\MemoryCommand::class );

Post-fix command map:

Command	Routes to
wp datamachine agent <verb>	AgentsCommand (new — aliased to plural)
wp datamachine agents <verb>	AgentsCommand (unchanged)
wp datamachine memory <verb>	MemoryCommand (unchanged — canonical home for memory ops)

Users can now reflexively type wp datamachine agent list, agent show, agent create — matching the muscle memory from every other noun — and get the expected dispatch instead of Error: 'list' is not a registered subcommand of 'datamachine agent'.

Breaking change

The singular memory-verb forms are gone:

wp datamachine agent read      → use wp datamachine memory read
wp datamachine agent write     → use wp datamachine memory write
wp datamachine agent search    → use wp datamachine memory search
wp datamachine agent paths     → use wp datamachine memory paths
wp datamachine agent sections  → use wp datamachine memory sections
wp datamachine agent compose   → use wp datamachine memory compose
wp datamachine agent daily ... → use wp datamachine memory daily ...
wp datamachine agent files ... → use wp datamachine memory files ...

Low blast radius per #1172's analysis: wp datamachine memory <verb> has been a registered alias for MemoryCommand since day one, so every caller has a stable replacement; the agent singular was never intuitive for memory ops (natural English is "agent's memory", not "agent read"); and external callers are small in number today.

Docs swept

• README.md — discovery command updated
• docs/overview.md — discovery command updated
• docs/core-system/wp-cli.md — agent section renamed to memory, alias list updated, workflow example migrated
• docs/core-system/wordpress-as-agent-memory.md — all path-discovery and memory-access snippets migrated (17 refs)
• docs/core-system/daily-memory-system.md — daily-memory CLI section migrated (6 refs)
• docs/core-system/ephemeral-workflows.md — stale reference fixed (agent → chat)
• inc/Cli/Commands/MemoryCommand.php — all 52 docblock examples + WP_CLI::error() usage strings migrated
• inc/Engine/AI/ComposableFileInvalidation.php — comment updated

docs/CHANGELOG.md left untouched per repo convention (homeboy generates it at release time from git commits).

Acceptance criteria

• wp datamachine agent list|create|show|delete|rename|access|config|export|import|token|cleanup-legacy-context-files route to AgentsCommand (aliased to plural)
• wp datamachine agents ... continues to work unchanged
• wp datamachine memory ... continues to work unchanged and is the canonical home for memory-file ops
• README + doc references to wp datamachine agent <memory-verb> updated to wp datamachine memory <verb>
• CHANGELOG left alone (generated from commit messages)

Commit message covers the breaking rename + points to the replacement; that becomes the user-facing changelog entry on release.

AI assistance

• AI assistance: Yes
• Tool(s): Claude Code (Opus 4.7)
• Used for: drafted the Bootstrap.php swap, swept doc references from wp datamachine agent <memory-verb> to wp datamachine memory <verb>, updated MemoryCommand docblocks/error strings. Chris filed the planning issue (CLI: unify datamachine agent / datamachine agents — one noun, one class (like every other DM noun) #1172) and greenlit the hard-swap path; I executed the mechanical changes against that plan.