fix(spur-spank): rename SPANK exports to Slurm-compatible symbols

[biluriuday]

Fix SPANK ABI and wire up plugin env/args (#294)

Existing Slurm SPANK plugins failed against Spur's host: the API symbols used a spur_spank_* prefix, and even after loading, plugins couldn't affect the job. This makes the SPANK host drop-in compatible with Slurm's spank.h.

What changed

ABI / symbol compatibility

• Renamed exports to Slurm's names and aligned signatures to spank.h: spank_get_item, spank_setenv (added the overwrite arg), plus new spank_getenv, spank_unsetenv, spank_job_control_{set,get,unset}env, spank_strerror, and the slurm_error/info/verbose/debug/debug2/debug3 + slurm_spank_log loggers.
• Fixed SpankItem discriminants to match Slurm's enum spank_item (previously mis-ordered, so S_JOB_ID returned the gid).
• Added ESPANK_* return codes; spank_get_item now returns ESPANK_NOT_AVAIL for known-but-unsupported items vs ESPANK_BAD_ARG for unknown ids.
• Made spurd export these symbols in its dynamic symbol table so dlopen'd plugins resolve them, via linker flags (--undefined + --export-dynamic, guarded on the target OS) in spurd/build.rs.

Functional wiring

• invoke_hook now threads a caller-owned SpankHandle, so plugin env edits persist and are visible across hooks/plugins.
• The executor seeds the handle from the job's env + context, runs Init/TaskInit after the env is assembled, and folds plugin env changes back into the launched job (both container and command paths).
• Plugstack arguments are now delivered to hooks as ac/argv (previously always 0/NULL).

Testing

• Unit/integration tests updated and extended (spur-spank + t58_spank): item-ID ordering, setenv overwrite semantics, getenv round-trip/errors, env-in seeding, NOT_AVAIL vs BAD_ARG.
• cargo clippy --workspace --exclude spur-ffi --all-targets clean.
• End-to-end on the bare-metal cluster: built a real SPANK plugin (slurm_spank_task_init) using spank_setenv/spank_get_item and a plugstack arg. Confirmed it loads (SPANK plugins loaded count=1) and a job sees the injected env (SPUR_SPANK_TEST=hello_from_spank, SPUR_SPANK_ARG=arg_from_plugstack).

Known limitations / follow-ups

• Logging functions are non-variadic (stable Rust can't define C-variadic fns), so printf-style format specifiers aren't expanded — the format string is logged verbatim.
• spank_get_item supports scalar items only (no S_JOB_ARGV/S_JOB_ENV or pid-to-id lookups).
• Hooks run in the spurd process, not the forked/privilege-dropped task.
• job_control_env isn't yet wired into prolog/epilog.
• Option-registration symbols (spank_option_register, etc.) are not yet provided.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 73.40720% with 96 lines in your changes missing coverage. Please review.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #429      +/-   ##
==========================================
+ Coverage   70.85%   71.99%   +1.14%     
==========================================
  Files         140      141       +1     
  Lines       41849    43196    +1347     
==========================================
+ Hits        29650    31095    +1445     
+ Misses      12199    12101      -98     

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[Copilot]

Pull request overview

Renames the SPANK host exports to Slurm-compatible spank_*/slurm_* symbols and adjusts ABI-facing signatures/IDs so existing Slurm SPANK plugins can resolve and call into Spur’s host process (spurd).

Changes:

• Add a spurd build script to export dynamic symbols for runtime dlopen/dlsym resolution.
• Align spur-spank exported symbol names, return codes, item IDs, and add basic env/job-control env helpers plus Slurm-style logging symbol stubs.
• Extend SPANK-focused tests to validate item ID discriminants and spank_setenv/spank_getenv behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
crates/spurd/build.rs	Adds linker argument emission to export dynamic symbols from the spurd binary.
crates/spur-tests/src/t58_spank.rs	Adds test coverage for Slurm item ID discriminants and env round-trip behavior.
crates/spur-spank/src/lib.rs	Renames exports to spank_*/slurm_*, aligns enums/return codes, adds env helpers + symbol retention anchor.

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[shiv-tyagi]

A few suggestions, all minor, nothing blocking. Symbol/enum ordering against spank.h looks correct and the tests are thorough. PTAL.