Add CLI command to send task input

[finallylly]

Summary

• Add kanban task send for sending follow-up input to running task sessions
• Support --text, stdin input, --project-path, and --no-submit
• Preserve Cline SDK message semantics while submitting terminal-backed agents with carriage return

Test plan

• npm run typecheck
• npm run test:precommit

[finallylly]

Usage examples:

# Send a follow-up prompt and submit it to the running task session
kanban task send \
  --project-path /path/to/workspace \
  --task-id <task-id> \
  --text "Please continue from the previous result"

# Type text into a terminal-backed session without pressing Enter
kanban task send \
  --project-path /path/to/workspace \
  --task-id <task-id> \
  --text "npm test" \
  --no-submit

# Read the follow-up text from stdin
printf 'What is 1+10?' | kanban task send \
  --project-path /path/to/workspace \
  --task-id <task-id>

[greptile-apps]

Greptile Summary

This PR adds a kanban task send CLI subcommand that delivers follow-up text to a running task session, with special handling for Cline (SDK message semantics — no carriage return) vs. terminal-backed agents (appends to submit). Previous review issues (stdin trailing-newline trim, empty --text guard) have been addressed.

Confidence Score: 5/5

Safe to merge — no blocking issues found; previously raised concerns have been addressed.

All code paths are guarded correctly (empty text, TTY stdin, trailing newline), agent-specific submit semantics are well-tested, and the two previously flagged issues (stdin double-submit and silent empty-text fall-through) are fixed.

No files require special attention.

Important Files Changed

Filename	Overview
src/commands/task.ts	Adds readStdinText, resolveSendTaskText, sendTaskInput, and the send subcommand registration; logic is sound with proper guards for empty text, TTY stdin, and Cline vs terminal-agent submission semantics.
test/runtime/task-command.test.ts	New test file covering the happy path, --no-submit, Cline skip-CR path, stdin trimming, and empty --text rejection — good coverage of the introduced code.

Sequence Diagram

sequenceDiagram
    participant CLI as CLI (task send)
    participant RST as resolveSendTaskText
    participant Stdin as process.stdin
    participant RT as runtimeClient

    CLI->>RST: resolve text (--text or stdin)
    alt --text provided and non-empty
        RST-->>CLI: text value
    else --text "" (empty)
        RST-->>CLI: throw Error
    else stdin (non-TTY)
        RST->>Stdin: read chunks
        Stdin-->>RST: raw bytes
        RST-->>CLI: text (trailing \n trimmed)
    else TTY, no --text
        RST-->>CLI: throw Error
    end

    CLI->>RT: sendTaskSessionInput(text, appendNewline=false)
    RT-->>CLI: {ok, summary: {agentId, ...}}

    alt submit=false OR agentId=cline
        CLI-->>User: {ok, submitted: input.submit}
    else terminal agent, submit=true
        CLI->>RT: sendTaskSessionInput("\r", appendNewline=false)
        RT-->>CLI: {ok, summary}
        CLI-->>User: {ok, submitted: true}
    end

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_{Reviews (4): Last reviewed commit: "Merge branch 'main' into feat/task-send-..." | Re-trigger Greptile}

[finallylly]

@greptile-apps please re-review