docs(bash): document the bashEnv hard dependency and dedupe the demo manifest

- tool-bash README (both languages) now shows the real four-service inject
  and attributes the session-persistence contributor to dsh-bash-env.
- pwsh-local README names the also-exported ENV_OVERRIDES/ENCODING_PREAMBLE.
- agent-spine-demo drops the duplicate bash-env devDependency key.

packages/bash/pwsh-local/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/bash/pwsh-local/README.md
-README.md: 76a30939d68ac866880f906b928b265628f4de1e
-README.zh.md: af98af1b83baa72ad8345362b583b61fa634d29a
+README.md: 9deba9c1b63ccfdb9e1805b9896db33f144839bf
+README.zh.md: e45c820e1d5e31aebd9ed365c6130850f1db2a62

packages/bash/pwsh-local/README.md

@@ -6,7 +6,7 @@ Local PowerShell implementation of the `@deepseek-ai/dsh-bash` executor seam ove
 
 The command string rides as ONE argv element to `-Command`: PowerShell itself parses the text, and no intermediate shell exists, so there is no shell-quoting layer to escape (the `bash -c` string domain has no equivalent here). Native Win32 paths (`C:\...`) pass through unchanged.
 
-The package root exports the default and named `PwshLocalExecutor` plugin, its `Config`, and the pure `resolvePwshPath`/`candidatePwshPaths` helpers.
+The package root exports the default and named `PwshLocalExecutor` plugin, its `Config`, the pure `resolvePwshPath`/`candidatePwshPaths` helpers, and the `ENV_OVERRIDES`/`ENCODING_PREAMBLE` constants the executor injects into every spawn.
 
 ## Config
 

packages/bash/pwsh-local/README.zh.md

@@ -6,7 +6,7 @@
 
 命令字符串作为 ONE argv 元素传给 `-Command`：由 PowerShell 自己解析文本，不存在中间 shell，因此没有需要转义的 shell 引号层（`bash -c` 字符串域在这里没有对应物）。原生 Win32 路径（`C:\...`）原样通过。
 
-包根导出默认与具名 `PwshLocalExecutor` 插件、其 `Config`，以及纯函数 `resolvePwshPath`/`candidatePwshPaths` 辅助函数。
+包根导出默认与具名 `PwshLocalExecutor` 插件、其 `Config`、纯函数 `resolvePwshPath`/`candidatePwshPaths` 辅助函数，以及执行器注入每次 spawn 的 `ENV_OVERRIDES`/`ENCODING_PREAMBLE` 常量。
 
 ## 配置