M1: parse .pdata RUNTIME_FUNCTION; cross-validate function boundaries

Adds an authoritative function-boundary source from the linker:
- New `xenia_xex::pdata` parses .pdata 8-byte entries (BeginAddress + packed
  prolog/length/flags). Bit layout per Microsoft PE32 PowerPC spec: prolog in
  bits 0..7, function_length in bits 8..29, flags in 30..31.
- `func::analyze_with_pdata` unions pdata BeginAddresses into the candidate
  set, attaches `pdata_validated`/`pdata_length` to each `FuncInfo`, and trims
  any function whose `end` overlaps the next start (catches mis-merge where
  one row spanned two prologues — the audit-031 sub_824D23B0/sub_824D29F0
  case).
- DB: extends `functions` with `pdata_validated BOOLEAN`, `pdata_length BIGINT`;
  new table `pdata_entries`; index on pdata_validated.
- New `crates/xenia-analysis/SCHEMA.md` documents M1 layer + forward work.

Validation on Sylpheed: 25481 functions (was 12156) / 23073 pdata_validated /
0 orphans / 0 mis-merges. Audit-031 mis-merge resolved: sub_824D29F0 now has
its own row with `pdata_length=280` (70 dwords); sub_824D23B0 now correctly
ends at 0x824D2878 (`pdata_length=1224` matches prologue walk).

Tests 605→610. New 5-test pdata unit suite covers bit layout + sentinel +
out-of-range filtering + real-world layout round-trip.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/xenia-analysis/tests/db_schema_golden.rs

@@ -65,12 +65,15 @@ fn synthetic_func_analysis(image_base: u32) -> FuncAnalysis {
             saved_gprs: 0,
             is_leaf: true,
             is_saverestore: false,
+            pdata_validated: false,
+            pdata_length: None,
         },
     );
     FuncAnalysis {
         functions,
         save_gpr_base: None,
         restore_gpr_base: None,
+        pdata_entries: Vec::new(),
     }
 }
 
@@ -154,6 +157,15 @@ fn db_schema_matches_expected_columns() {
             ("saved_gprs", "BIGINT"),
             ("is_leaf", "BOOLEAN"),
             ("is_saverestore", "BOOLEAN"),
+            ("pdata_validated", "BOOLEAN"),
+            ("pdata_length", "BIGINT"),
+        ]),
+        ("pdata_entries", &[
+            ("begin_address", "BIGINT"),
+            ("end_address", "BIGINT"),
+            ("function_length", "BIGINT"),
+            ("prolog_length", "BIGINT"),
+            ("flags", "BIGINT"),
         ]),
         ("labels", &[
             ("address", "BIGINT"),