chore(fpga): de-hardcode AUTO_FLASH.sh foreign paths + parameterize cable

[gHashTag]

Goal

Make fpga/AUTO_FLASH.sh runnable on any checkout by replacing /Users/playra/trinity-w1/... with SCRIPT_DIR-relative paths and parameterizing the JTAG cable so it drives the AX7203 onboard FTDI + openFPGALoader, not only the Platform Cable USB II.

Context

Now that the FPGA is physically connected, P0 (toolchain bring-up + first real flash) is unblocked — but the flash scripts still assume a foreign machine. fpga/AUTO_FLASH.sh hardcodes /Users/playra/trinity-w1/fpga/... for BITFILE, TOOLS, TEST_BIN and a cd (confirmed lines 8-10, 42), so it cannot run on this checkout (user ssdm4, repo at /Users/ssdm4/Desktop/PROJECTS/CLAUDE/trinity). fpga/flash.sh and fpga/xvc_flash.sh already use SCRIPT_DIR and are the correct template. The same playra foreign paths and a Platform-Cable-only workflow also leak into fpga/JTAG_TROUBLESHOOTING.md (lines 16/22/27/36/76) and fpga/FLASH_HISTORY.md, including a playra ALL=(ALL) NOPASSWD sudoers block (lines 82-84) that assumes a specific user.

The flash flow is also cable-locked: AUTO_FLASH.sh hardwires the fxload (03fd:0013 → 0x0008) + jtag_program ritual for the Xilinx Platform Cable USB II clone. The connected AX7203 (xc7a200t) uses an onboard FTDI USB-JTAG (typ. 0403:6010), which jtag_program does not support — COMMON_PITFALLS.md directs FTDI cables to openFPGALoader (gHashTag fork). So the script must select the cable/tool per board. This issue is scripts + docs only — no new board defs or bitstreams (those are separate P0 issues).

Tasks

• fpga/AUTO_FLASH.sh: add SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)" and derive BITFILE/TOOLS/TEST_BIN from it (mirror fpga/flash.sh / fpga/xvc_flash.sh); remove the hardcoded cd /Users/playra/trinity-w1/fpga/openxc7-synth.
• Parameterize cable via a CABLE/FLASH_TOOL env var (or --cable): default platform-usb-ii = existing fxload+jtag_program path; add ft2232/openfpgaloader = openFPGALoader --cable ft2232 --write <bit> (no fxload, no unplug/replug). Make BITFILE overridable via arg/env so it is not pinned to vsa_uart_top.bit.
• Guard the fxload/reconnect prompt so it only runs for the Platform-Cable path (FTDI needs neither firmware upload nor reconnect).
• fpga/JTAG_TROUBLESHOOTING.md: rewrite /Users/playra/trinity-w1/... (lines 16/22/27/36/76) to SCRIPT_DIR-relative / fpga/... paths; add a short "FTDI / AX7203 → use openFPGALoader" note so the doc is no longer Platform-Cable-only.
• fpga/FLASH_HISTORY.md: replace /Users/playra/trinity-w1/... command paths and drop the playra ALL=(ALL) NOPASSWD sudoers block (lines 82-84) / user assumption; note sudo is only needed for the Platform-Cable USB path, not FTDI/openFPGALoader.
• grep -rn '/Users/playra\|trinity-w1\|NOPASSWD' fpga/ returns nothing after the edits.
• Smoke-run bash fpga/AUTO_FLASH.sh from a fresh clone with CABLE=openfpgaloader and confirm it resolves paths and reaches the flash step without a hardcoded-path failure.

Acceptance criteria

• grep -rn '/Users/playra\|trinity-w1' fpga/AUTO_FLASH.sh fpga/JTAG_TROUBLESHOOTING.md fpga/FLASH_HISTORY.md → 0 hits.
• grep -rn 'NOPASSWD' fpga/ → 0 hits.
• bash fpga/AUTO_FLASH.sh run from an arbitrary clone path resolves BITFILE/TOOLS/TEST_BIN relative to the script (no absolute foreign path in output).
• CABLE=openfpgaloader BITFILE=<blink.bit> bash fpga/AUTO_FLASH.sh invokes openFPGALoader (not fxload/jtag_program) and does not prompt for a cable reconnect.
• Default (unset CABLE) still executes the proven fxload → reconnect → jtag_program Platform-Cable path unchanged.

Dependencies

None — this is a standalone P0 hygiene fix and a prerequisite for the AX7203 first-flash gate (the openFPGALoader/FTDI board-bring-up issue) and shares the playra-path defect class with the fpga-synth SKILL.md fix.

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