refactor(web): project usage and snapshot request context

packages/llm/token-meter/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/llm/token-meter/README.md
-README.md: 578728ded9cf51a12abcd70d541404e995028f26
-README.zh.md: 51518e98c43e740822970c1a39154f550ea962dc
+README.md: 5ab1315d8f5885fb24ea48d4e97b7ab9a596483c
+README.zh.md: 063370e90cd01414e899bbde76a68dc3b603c06b

packages/llm/token-meter/README.md

@@ -21,6 +21,12 @@ The fold tracks full request-header snapshots, step boundaries, surface appends
 
 Usage accounting sums disjoint input, cache-read, cache-write, and output buckets; reasoning is not added again. Every successful call records an assistant anchor, including content-less calls. An explicit empty provenance list means a known empty provider stream, while absent legacy provenance conservatively treats the durable assistant output as provider output.
 
+## Session projection
+
+When the composition provides `ctx.sessionProjections`, token-meter registers the `tokenUsage` unit through an optional child fiber. Its client-safe value is the complete durable log's `uncachedInputTokens`, `outputTokens`, `cacheReadTokens`, and `cacheWriteTokens`. Usage chunks are counted even when a request later fails; a final assistant-message usage for the same `(turn, step)` replaces that sample instead of double-counting it. Reasoning remains an output subdivision.
+
+The unit uses the standard projection baseline, live frame, higher-seq-wins store, and JSON checkpoint paths. Unloading token-meter removes the key. A headless or TUI composition without the projection seam keeps the measurement service's existing behavior.
+
 ## Composition
 
 ```yaml

packages/llm/token-meter/README.zh.md

@@ -21,6 +21,12 @@ fold 跟踪完整请求标头快照、步骤边界、表层追加与替换、成
 
 用量计量会求和不重叠的输入、cache-read、cache-write 与输出 bucket；不会再次添加 reasoning。每次成功调用都会记录一个 assistant 锚点，包括无内容调用。显式空溯源列表表示已知空提供方流，而缺失的遗留溯源会保守地将持久 assistant 输出视为提供方输出。
 
+## 会话投影
+
+当组合提供 `ctx.sessionProjections` 时，token-meter 会通过一个可选子 fiber 注册 `tokenUsage` 单元。其可安全传给客户端的值包含完整持久日志中的 `uncachedInputTokens`、`outputTokens`、`cacheReadTokens` 和 `cacheWriteTokens`。即使请求随后失败，用量分片仍会计入；同一 `(turn, step)` 的最终 assistant 消息用量会替换该样本，而不是重复计数。推理仍是输出的一个细分项。
+
+该单元使用标准的投影基线、实时帧、seq 高者胜值仓和 JSON 检查点路径。卸载 token-meter 会移除该键。不带投影 seam 的 headless 或 TUI 组合会保留测量服务的既有行为。
+
 ## 组合
 
 ```yaml

packages/llm/token-meter/package.json

@@ -17,7 +17,7 @@
     },
     "./client": {
       "types": "./lib/types/client.d.ts",
-      "default": "./lib/client.js"
+      "default": "./lib/types/client.js"
     },
     "./src/*": "./src/*",
     "./package.json": "./package.json"
@@ -25,7 +25,7 @@
   "files": [
     "lib/index.js",
     "lib/invariant.js",
-    "lib/client.js",
+    "lib/types/**/*.js",
     "lib/types/**/*.d.ts",
     "lib/types/**/*.d.ts.map",
     "src"