Persistent pwsh keeps the backend's controlled prompt
持久 pwsh 保留后端的受控提示符
`dsh-tool-pwsh-persistent` initialized its shell with a `prompt` function of its own (`'__DSH_PERSISTENT_PWSH_PROMPT__ '`), overwriting the `prompt` that `dsh-terminal-bash` installs in its pwsh startup sequence. The backend's prompt readiness requires the printable tail after the OSC `133;D` marker to exactly equal the controlled `dsh> ` prompt ([design](../feature/2026-07-16-persistent-pty-sessions.md)), so after i
English
Problem
dsh-tool-pwsh-persistent initialized its shell with a prompt function of its own ('__DSH_PERSISTENT_PWSH_PROMPT__ '), overwriting the prompt that dsh-terminal-bash installs in its pwsh startup sequence. The backend's prompt readiness requires the printable tail after the OSC 133;D marker to exactly equal the controlled dsh> prompt (design), so after initialization no send could settle through it and every send paid the silence tier plus handoff grace. Measured on Windows through the real Loader composition with production defaults: 8493 ms for the first call (spawn, initialization, and command) and 3722/3832/3759 ms for the next three, against 1340/255/251/241 ms with the controlled prompt intact. The package tests masked it by configuring idleSilenceMs: 300.
The persistent bash tool fixed the identical defect by giving up its own prompt override; the pwsh twin kept it. The override served the same two consumers there: a viewport-suffix fallback detecting "shell at a prompt without the end marker", and cosmetic stripping of prompt text from partial output.
Decision
The tool no longer installs a prompt. dsh-terminal-bash owns the pwsh prompt function, installs it during spawn, and returns the session only after that startup reached stdin_read readiness, so the tool's initialization send had nothing left to establish and is deleted together with its PWSH_PROMPT_SETUP command.
The viewport-suffix fallback is replaced with the seam's own signal: a send that settles as stdin_read without the end marker in scrollback returns the captured partial output. The private prompt constant and its stripping are deleted; partial output may now end with the backend's own prompt text, which the tool cannot and should not know. stripPrompt collapses to trimTrailingNewline, matching dsh-tool-bash-persistent.
Alternatives considered
Align the tool's prompt text with the backend's dsh> . Rejected: it keeps a second installation of one protocol constant and a second owner of it, and the send is redundant because the backend had already installed the identical prompt before spawn resolved.
Import the controlled prompt into the tool. Rejected: the prompt is one provider's protocol constant; a Consumer matching it would couple the tool to dsh-terminal-bash specifically, and any other mounted pwsh-dialect backend would break it again.
Lower handoffGraceMs/idleSilenceMs instead. Rejected: no silence value fixes a dead fast path; it rebalances how much every call overpays, and the silence tier is also what absorbs a genuinely broken prompt.
Re-assert the pwsh prompt per prompt, as PROMPT_COMMAND does for bash. Rejected: PowerShell has no per-prompt hook outside the prompt function itself, so a redefinition cannot be healed the way bash's variable is; the residue stays a documented limitation.
Consequences
Windows, production defaults, real Loader composition: tool calls drop from 8493/3722/3832/3759 ms to 1340/255/251/241 ms (spawn + initialization + first command, then three warm commands).
The stdin_read fallback is behavior, not only cosmetics: where a provider proves a foreground stdin wait, an interactive child returns captured partial output instead of spinning to the command deadline, and elsewhere the call still runs to timeoutMs. That early return keeps the session, so a child still reading stdin can consume the next call's command until that call reaches timeoutMs and resets the shell; dsh-tool-bash-persistent behaves the same way, and distinguishing the shell's own prompt readiness from a child's stdin wait belongs to the seam rather than to either tool. Complete marker-delimited output is unchanged.
The loader-composition suite records every send's waitReason and requires at least six stdin_read settlements and no inferred_idle: the regression is reported by the settle reason itself, not by how long silence takes. Reinstating the removed prompt override fails that assertion after 30 s with expected 0 to be greater than or equal to 6, while the case's output assertions still pass. The stub suite drops the initialization-handshake modes and pins the prompt text retained in partial output instead of its absence.
A model command that redefines prompt still removes the readiness marker and degrades later sends to the silence tier: the backend installs its prompt once at startup and cannot re-assert it.
中文
Problem
dsh-tool-pwsh-persistent 用自己安装的 prompt 函数（'__DSH_PERSISTENT_PWSH_PROMPT__ '）初始化其 shell，覆盖了 dsh-terminal-bash 在 pwsh 启动序列中安装的 prompt。后端的提示符就绪检测要求 OSC 133;D 标记之后的可打印尾部与受控提示符 dsh> 完全相等（设计），因此初始化之后任何 send 都无法经由该路径结算，每次 send 都要支付静默层加交接宽限。在 Windows 上通过真实 Loader 组合以生产默认值实测：首次调用（spawn、初始化与命令）8493 毫秒，随后三次为 3722/3832/3759 毫秒；受控提示符完好时为 1340/255/251/241 毫秒。包测试把 idleSilenceMs 配成 300，掩盖了该问题。
持久 bash 工具已修复同一缺陷，方式是放弃自己的提示符覆盖；pwsh 孪生工具保留了它。该覆盖在两个工具中服务同样的两个消费点：用视口后缀检测「shell 已回到提示符但没有结束标记」的回退判定，以及从部分输出中剥离提示符文本的美化。
Decision
工具不再安装提示符。pwsh 的 prompt 函数由 dsh-terminal-bash 拥有，在 spawn 期间安装，且只在该启动流程达到 stdin_read 就绪后才返回会话，因此工具的初始化 send 已无可确立之事，与其 PWSH_PROMPT_SETUP 命令一并删除。
视口后缀回退替换为 seam 自己的信号：一次以 stdin_read 结算而 scrollback 中没有结束标记的 send，返回已捕获的部分输出。私有提示符常量及其剥离逻辑删除；部分输出现在可能以后端自己的提示符文本结尾，工具无法也不应知道该文本。stripPrompt 收敛为 trimTrailingNewline，与 dsh-tool-bash-persistent 一致。
Alternatives considered
把工具的提示符文本对齐到后端的 dsh> 。 被拒绝：这保留了同一个协议常量的第二份安装与第二个拥有者，而且该 send 是多余的——后端在 spawn 返回前就已安装相同的提示符。
把受控提示符导入工具。 被拒绝：提示符是单个提供方的协议常量；Consumer 匹配它就把工具与 dsh-terminal-bash 具体耦合，换任何其他 pwsh 方言后端都会再次损坏。
改为调小 handoffGraceMs/idleSilenceMs。 被拒绝：任何静默值都修不好已死的快速路径，只是重新分配每次调用多付多少；而静默层同时也是吸收真正损坏提示符的那一层。
像 bash 的 PROMPT_COMMAND 那样在每个提示符处重新设定 pwsh 提示符。 被拒绝：除 prompt 函数本身之外，PowerShell 没有每提示符钩子，因此重定义无法像 bash 的变量那样被治好；该残余已记入已知限制。
Consequences
Windows、生产默认值、真实 Loader 组合：工具调用从 8493/3722/3832/3759 毫秒降至 1340/255/251/241 毫秒（spawn + 初始化 + 首条命令，随后三条热命令）。
stdin_read 回退是行为而不只是美化：在提供方能证明前台 stdin 等待之处，交互式子进程会返回已捕获的部分输出，而不是空转到命令期限；其他情况下调用仍会运行到 timeoutMs。该提前返回保留会话，因此仍在读取 stdin 的子进程可能吞掉下一次调用的命令，直到那次调用到达 timeoutMs 并重置 shell；dsh-tool-bash-persistent 行为相同，而区分「shell 自身的提示符就绪」与「子进程的 stdin 等待」属于 seam，而不是任一工具。由标记界定的完整输出保持不变。
loader 组合套件记录每次 send 的 waitReason，要求至少六次 stdin_read 且没有 inferred_idle：回归由结算原因本身报告，而不是靠静默层耗时。把删掉的提示符覆盖加回去，该断言会在 30 秒后以 expected 0 to be greater than or equal to 6 失败，而同一用例的输出断言仍然通过。stub 套件删除了初始化握手模式，并改为锚定部分输出中保留的提示符文本，而不是它的缺席。
重定义 prompt 的模型命令仍会移除就绪标记，并把后续 send 降级到静默层：后端只在启动时安装一次提示符，无法重新设定。