docs(02-02): complete tier 1 medium/low-confidence providers plan

.planning/phases/02-tier-1-2-providers/02-02-SUMMARY.md

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+---
+phase: 02-tier-1-2-providers
+plan: 02
+subsystem: providers
+tags: [providers, yaml, tier-1, keyword-anchoring]
+requires: [pkg/providers/schema.go, pkg/providers/loader.go, pkg/providers/registry.go]
+provides:
+  - Azure OpenAI 32-hex pattern provider definition
+  - Meta AI (Llama API) LLM|-prefixed token provider definition
+  - Cohere 40-char token provider definition
+  - Mistral AI 32-char keyword-anchored provider definition
+  - Inflection AI (Pi) opaque-token provider definition
+  - AI21 Labs 32+-char keyword-anchored provider definition
+affects: [providers/, pkg/providers/definitions/]
+tech_stack:
+  added: []
+  patterns: [yaml-provider-definitions, dual-location-embed, keyword-ac-prefilter]
+key_files:
+  created:
+    - providers/azure-openai.yaml
+    - providers/meta-ai.yaml
+    - providers/cohere.yaml
+    - providers/mistral.yaml
+    - providers/inflection.yaml
+    - providers/ai21.yaml
+    - pkg/providers/definitions/azure-openai.yaml
+    - pkg/providers/definitions/meta-ai.yaml
+    - pkg/providers/definitions/cohere.yaml
+    - pkg/providers/definitions/mistral.yaml
+    - pkg/providers/definitions/inflection.yaml
+    - pkg/providers/definitions/ai21.yaml
+  modified: []
+decisions:
+  - Low-confidence regex (generic character classes) compensated by strong keyword lists for Aho-Corasick pre-filtering
+  - Azure OpenAI and Inflection use empty verify blocks (no stable public endpoint / requires deployment URL)
+  - Meta AI pattern anchors on LLM| literal prefix to reduce false positives
+metrics:
+  duration: 1m
+  tasks: 2
+  files: 12
+  completed: "2026-04-05T11:11:55Z"
+requirements: [PROV-01]
+---
+
+# Phase 2 Plan 2: Tier 1 Medium/Low-Confidence Providers Summary
+
+Added 6 Tier 1 LLM provider YAML definitions (Azure OpenAI, Meta AI, Cohere, Mistral, Inflection, AI21) with strong keyword lists anchoring generic opaque-token regex patterns, completing Tier 1 at 12/12.
+
+## What Was Built
+
+Created 12 YAML files (6 providers x dual location) covering the remaining Tier 1 providers that lack distinctive high-confidence prefix patterns. These providers rely on Aho-Corasick keyword pre-filtering (azure, cohere, mistral, jamba, PI_API_KEY, etc.) to reduce false positives since their key formats are opaque hex/alphanumeric tokens.
+
+- **Azure OpenAI**: 32-hex pattern, no verify endpoint (requires per-deployment URL)
+- **Meta AI**: `LLM|` literal prefix anchor, api.llama.com verify endpoint
+- **Cohere**: 40-char alphanumeric, api.cohere.ai verify endpoint
+- **Mistral AI**: 32-char alphanumeric, api.mistral.ai verify endpoint
+- **Inflection AI**: 40+-char token, no public verify endpoint
+- **AI21 Labs**: 32+-char alphanumeric, api.ai21.com/studio verify endpoint
+
+All providers dual-located for Go embed.FS (pkg/providers/definitions/) and user visibility (providers/). Registry loader test passes with all 9 providers (3 existing + 6 new).
+
+## Tasks Completed
+
+| Task | Name                                    | Commit  | Files |
+|------|-----------------------------------------|---------|-------|
+| 1    | Azure OpenAI, Meta AI, Cohere YAMLs     | bca8422 | 6     |
+| 2    | Mistral, Inflection, AI21 YAMLs         | adad602 | 6     |
+
+## Verification
+
+- `go test ./pkg/providers/... -count=1` -- PASS (0.037s)
+- `diff` on all 6 provider pairs -- no drift between providers/ and pkg/providers/definitions/
+- `grep -l 'tier: 1' providers/*.yaml | wc -l` -- 12 (matches Tier 1 complete criterion)
+
+## Deviations from Plan
+
+None - plan executed exactly as written.
+
+## Decisions Made
+
+- **Empty verify blocks for Azure OpenAI and Inflection**: Azure OpenAI requires per-deployment URL (`https://{resource}.openai.azure.com/...`) which cannot be hardcoded; Inflection lacks a stable public verify endpoint. Both use empty `url: ""` and empty status arrays to signal "verification unsupported" for Phase 5.
+- **Low confidence on all 6**: Generic character-class regex patterns would cause high false-positive rates without keyword anchoring, so confidence is marked `low` and the AC automaton carries the detection weight.
+
+## Key Links
+
+- Provider `keywords[]` feeds `NewRegistry()` which builds the Aho-Corasick DFA across all providers
+- Aho-Corasick pre-filter gates per-pattern regex evaluation (established in Phase 01)
+
+## Self-Check: PASSED
+
+All 12 files verified present:
+- providers/{azure-openai,meta-ai,cohere,mistral,inflection,ai21}.yaml -- FOUND
+- pkg/providers/definitions/{azure-openai,meta-ai,cohere,mistral,inflection,ai21}.yaml -- FOUND
+
+Commits verified:
+- bca8422 -- FOUND
+- adad602 -- FOUND