Skip ENDBR64 in invalid-op exceptions, add SS to InterruptFrame, and show ELF load progress

[pradosh-arduino]

Motivation

• Fix false-positive invalid-op exceptions caused by Intel CET ENDBR64 instruction and expose the stack segment in interrupt dumps.
• Provide visual progress feedback when loading ELF program headers from VFS.
• Remove in-place ELF relocation application to simplify the loader path used by this build.

Description

• Add ss to InterruptFrame and reorder saved registers in source/includes/isr.h so the interrupt frame captures the stack segment.
• Add skip_endbr64_if_present in source/kernel/C/interrupts/isr.c and call it from the invalid-op (#UD) handler to detect and skip a leading ENDBR64 (bytes F3 0F 1E FA) when running in user mode.
• Add elf_log_load_progress to source/kernel/C/executables/elf.c and invoke it during VFS-based program header staging to print a textual progress bar and percent for each segment loaded.
• Remove the in-file relocation application functions (elf_apply_relocation_entries, elf_apply_relocations_from_memory, elf_apply_relocations_from_vfs) and related calls so relocations are no longer applied during the current ELF load paths.
• Update source/kernel/C/meltdown.c to print the new SS field in the interrupt_frame_dump output.

Testing

• Built the kernel with make successfully.
• Ran the automated QEMU boot script (make qemu) which reached the kernel prompt and exercised the ELF loader path that emits the new progress output.
• No build errors or regressions were observed in the exercised boot/load scenario.

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Codex Task