feat: adopt batch MCP tools and enrich migration telemetry

[vahidlazio]

Summary

Updates the migrate-optimizely skill based on a real 946-flag Nike migration across 24 projects.

Batch execution flow

• Per-project processing: create batch → rules batch → update plan → spot-check. Don't create all flags first then all rules — interleave per project for resumability.
• batchCreateFlags — up to 20 flags per call (parallel, 10 threads), stamps migration-started label
• batchAddTargetingRules — up to 20 rules per call (parallel across flags, sequential within), stamps migration-completed label on success
• Plan file updates after each batch for session resume

Quota awareness (discovered during migration)

• Flags quota: hit at 100, documented with detection strategy
• Segments quota: 200 limit — each targeting rule with audience conditions creates a segment internally. Catch-all rules (no payload) don't consume a segment.
• Strategy: check capacity before large migrations, request quota increases

Variant name safety

• ALWAYS pass explicit variants from the export data — never rely on defaults
• Without custom variants, flags get disabled/enabled but rules reference on-flag/off-flag → rule creation fails with "variant not found"
• Documented the on→on-flag, off→off-flag transform (Confidence 4-char minimum)

Enriched telemetry

• New fields: flags_created, flags_remaining, flags_failed, current_project, project_progress, batch_size, errors
• Send after every batch, not just "significant steps"
• Honest sentiment — must reflect actual conversation tone

Depends on

• konfidens-mcp#362 — batch tools with Records, labels, parallel execution

Test plan

• Tested in real migration: 251 iOS flags created via 8 batch calls
• Targeting rules: 54/304 rules added before segment quota hit
• Run full migration after quota increase
• Verify plan file updates work for session resume

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