Add the existing pibot environment to official releases

[abcpibot]

FluidDial already carries [env:pibot] for the PiBot Pendant V4 (added in #51, with the FT5x06 polling fix in #61), but buildRelease.yml and manifest.py still only ship m5dial and cyddial. So there is no prebuilt PiBot image in an official release, and PiBot users have to build from source or get a binary elsewhere.

This adds the environment that already exists to the release, nothing more.

Changes

• .github/workflows/buildRelease.yml — build loop m5dial cyddial → m5dial cyddial pibot
• manifest.py — copy pibot into the release directory, and offer it as a second esp32 firmware variant alongside the CYD build

No source, board, or platformio.ini changes: [env:pibot] is already there and already extends env:cyd_base, so it needs no new toolchain or partition setup.

Manifest layout

PiBot lands next to CYD under the existing esp32 node; M5Dial is untouched under esp32s3.

Processor type
├── esp32 (ESP32-WROOM)
│   ├── FluidDial for CYD          → cyddial
│   └── FluidDial for PiBot Pendant V4  → pibot   ← new
└── esp32s3 (ESP32-S3-WROOM-1)
    └── FluidDial for M5Dial       → m5dial

Verification

Ran the exact build loop and manifest.py from this branch in CI (release/deploy steps omitted, since those need repo secrets):

• all three environments compile
• release/ contains m5dial.bin (8.0M), cyddial.bin (4.0M), pibot.bin (4.0M), manifest.json
• manifest.json validates: every image referenced by an installable exists on disk and its recorded size matches the file
• pibot is reachable as an installable

The resulting pibot.bin is a complete merged image (0xE9 bootloader at 0x1000, flashable at 0x0), and an equivalent build has been flash-tested on PiBot Pendant V4 hardware.