refactor(client-ui-plugin-config): stage card edits behind an explicit save

Controls committed on blur, which turned leaving a field into a durable,
revision-fenced document write the user could neither preview nor undo, and
silently discarded a draft the field did not accept.

A card's form now owns the staged text every control renders, and Save is the
only point where drafts become writes. Reset stages the composed default the
same way; an invalid draft blocks the save with its reason instead of being
dropped; Discard drops the drafts; a collapsed card marks that it holds some.
The Host stays the only authority on whether a value was accepted, so the save
reads the section back and keeps the drafts of a save that did not land.

apps/web/tests/plugin-config.e2e.ts

@@ -85,7 +85,7 @@ describe('web e2e: plugin configuration section', () => {
     expect(tripwire.pageErrors).toEqual([])
   }, 60_000)
 
-  it('writes an edited field to the settings document and marks it overridden', async () => {
+  it('stages an edit and writes it only when saved', async () => {
     onTestFailed(() => saveFailureShot(page, 'web-e2e-plugin-config-write'))
     const dialog = await openPlugins()
     await dialog.getByText('终端', { exact: true }).click()
@@ -97,12 +97,52 @@ describe('web e2e: plugin configuration section', () => {
     await timeout.fill('12000')
     await timeout.blur()
 
+    // Nothing crosses the wire until the user saves: leaving the control is
+    // not a decision to store the value.
+    expect(await settingsDocument()).not.toContain('timeoutMs')
+    const save = dialog.getByRole('button', { name: '保存', exact: true })
+    await expect.poll(() => save.isEnabled(), { timeout: 5_000 }).toBe(true)
+    await save.click()
+
     await expect.poll(async () => (await settingsDocument()).includes('timeoutMs: 12000'), { timeout: 10_000 })
       .toBe(true)
     // Presence in the user layer is what the badge reports, and the reset is
     // offered only for a field that has one.
     await expect.poll(() => dialog.getByText('已覆盖').count(), { timeout: 5_000 }).toBe(1)
     expect(await dialog.getByRole('button', { name: '恢复默认' }).count()).toBe(1)
+    // A settled form offers no save to repeat.
+    await expect.poll(() => save.isDisabled(), { timeout: 5_000 }).toBe(true)
+    expect(tripwire.pageErrors).toEqual([])
+  }, 60_000)
+
+  it('drops a staged edit on discard without touching the document', async () => {
+    onTestFailed(() => saveFailureShot(page, 'web-e2e-plugin-config-discard'))
+    const dialog = await openPlugins()
+    await dialog.getByText('终端', { exact: true }).click()
+    const timeout = dialog.getByLabel('命令超时（毫秒）')
+    await timeout.waitFor({ timeout: 10_000 })
+
+    await timeout.fill('7000')
+    await dialog.getByRole('button', { name: '放弃修改' }).click()
+
+    await expect.poll(() => timeout.inputValue(), { timeout: 5_000 }).toBe('12000')
+    expect(await settingsDocument()).toContain('timeoutMs: 12000')
+    expect(tripwire.pageErrors).toEqual([])
+  }, 60_000)
+
+  it('refuses to save a draft that is not a number', async () => {
+    onTestFailed(() => saveFailureShot(page, 'web-e2e-plugin-config-invalid'))
+    const dialog = await openPlugins()
+    await dialog.getByText('终端', { exact: true }).click()
+    const timeout = dialog.getByLabel('命令超时（毫秒）')
+    await timeout.waitFor({ timeout: 10_000 })
+
+    await timeout.fill('soon')
+
+    const save = dialog.getByRole('button', { name: '保存', exact: true })
+    await expect.poll(() => save.isDisabled(), { timeout: 5_000 }).toBe(true)
+    expect(await dialog.getByText('请填数字；留空表示使用默认值。').count()).toBe(1)
+    await dialog.getByRole('button', { name: '放弃修改' }).click()
     expect(tripwire.pageErrors).toEqual([])
   }, 60_000)
 
@@ -114,11 +154,17 @@ describe('web e2e: plugin configuration section', () => {
     await timeout.waitFor({ timeout: 10_000 })
     expect(await timeout.inputValue()).toBe('12000')
 
+    // The reset stages the composed default; the document still carries the
+    // override until the save lands.
     await dialog.getByRole('button', { name: '恢复默认' }).click()
+    await expect.poll(() => timeout.inputValue(), { timeout: 5_000 }).toBe('60000')
+    expect(await settingsDocument()).toContain('timeoutMs: 12000')
+
+    await dialog.getByRole('button', { name: '保存', exact: true }).click()
 
     await expect.poll(async () => (await settingsDocument()).includes('timeoutMs'), { timeout: 10_000 })
       .toBe(false)
-    await expect.poll(() => timeout.inputValue(), { timeout: 5_000 }).toBe('60000')
+    expect(await timeout.inputValue()).toBe('60000')
     expect(await dialog.getByText('已覆盖').count()).toBe(0)
     expect(tripwire.pageErrors).toEqual([])
   }, 60_000)