fix(tui): handle spacebar in turn-running input viewport

[Desperado]

Problem

When the agent is processing a task and the user types a new message in the chat terminal, spaces are silently dropped — the message appears without spaces (e.g. helloworld instead of hello world).

Root cause

Bubble Tea v1.3.10 delivers the spacebar as tea.KeySpace, not tea.KeyRunes (bubbletea/key.go:699-701):

if len(runes) == 1 && runes[0] == ' ' {
    k.Type = KeySpace
}

The idle input widget (input.go:289) already handles tea.KeySpace correctly. But the turn-running viewport (turnViewportModel.updateKey) had no case tea.KeySpace — every space fell through to the default return m, nil and was dropped.

Fix

Added the missing case tea.KeySpace handler in turn_viewport.go that inserts ' ' at the cursor position, matching the rune-insert pattern used by the rest of the switch.

Test

Added regression test TestTurnViewportInsertsSpaceKey — verified it fails without the fix (text = "helloworld") and passes with it (text = "hello world").

=== RUN   TestTurnViewportInsertsSpaceKey
--- PASS: TestTurnViewportInsertsSpaceKey (0.00s)

All existing TestTurnViewport* tests still pass.

[sigilix]

Sigilix Overview

Effort: 2/5 (small)

Quality gates

• ✅ PR title follows convention
• ✅ PR description is complete
• ℹ️ PR is linked to an issue — No Closes #N / Closes SIG-N keyword found in PR body or commit messages.

Summary — latest push

Fixes a bug where spacebar input was silently dropped in the turn-running viewport by adding a missing tea.KeySpace case that inserts a space character at the cursor. The implementation correctly mirrors the existing rune-insertion pattern used for other characters, and a targeted regression test validates the fix.

Important files

File	Score	Notes	Next step
internal/tui/turn_viewport.go	4/5	Adds the missing tea.KeySpace handler to updateKey so spacebar presses insert a space rune at the cursor instead of falling through to the default no-op return.	Extract the shared slice-shift-and-insert logic used here and in tea.KeyRunes into a helper method to eliminate the copy-paste mutation pattern.
internal/tui/turn_viewport_test.go	3/5	Adds a regression test verifying that tea.KeySpace followed by tea.KeyRunes produces the expected spaced string instead of concatenated output.	Add a test case for inserting a space in the middle of existing text to ensure the cursor and slice copy logic hold for non-append positions.

Confidence: 5/5

The change is a narrow, well-tested bug fix that aligns exactly with the existing input-handling pattern and carries zero risk of data corruption or side effects.

• Verify the slice-shift logic in turn_viewport.go lines 239-241 correctly handles mid-string space insertion, not just appends, since copy behavior differs when m.cursor < len(m.text).
• Confirm that tea.KeySpace is the only key type Bubble Tea remaps from tea.KeyRunes that this switch is missing (e.g., no other whitespace keys like tab are affected).

Suggested labels: bug

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