refactor(frontend): preserve config source in GuiConfigService instead of one flat map

[Ma77Ball]

Stacked on #5545 (adds the /config/amber endpoint and the amber config source this PR namespaces). Base diff includes #5545 until it merges; review the last commit only, or after #5545 lands. Kept as a draft for that reason.

What changes were proposed in this PR?

• Changed GuiConfigService to store each endpoint's payload under its own key in a configBySource map (preLogin, gui, amber, userSystem) instead of spreading them all into one flat object, so the origin of every config value is preserved (addresses the review comment on refactor(config): unify default-data-transfer-batch-size into one config key #5545).
• Derived the existing flat env getter from configBySource on read, keeping its shape identical so the ~50 existing guiConfigService.env.<flag> call sites are untouched.
• Added a source(name) accessor that returns one endpoint's payload in isolation.
• Added unit tests for the isolation guarantees (each source retrievable alone, no key bleed across sources, empty object for an unloaded source).

Any related issues, documentation, discussions?

Closes: #5669

How was this PR tested?

• Run cd frontend && npx ng test --include="src/app/common/service/gui-config.service.spec.ts" and expect 11 passed (8 existing merge/orchestration tests plus 3 new source-isolation tests).
• Confirm the merged view is unchanged: service.env.defaultDataTransferBatchSize still resolves after post-login load, while service.source("amber") returns only the amber payload and service.source("gui") does not contain defaultDataTransferBatchSize.

Was this PR authored or co-authored using generative AI tooling?

Co-authored with Claude Opus 4.8 in compliance with ASF

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 53.04%. Comparing base (7ae9b35) to head (6b68a32).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #5673      +/-   ##
============================================
- Coverage     53.12%   53.04%   -0.09%     
- Complexity     2544     2545       +1     
============================================
  Files          1075     1075              
  Lines         42232    41743     -489     
  Branches       4604     4514      -90     
============================================
- Hits          22436    22141     -295     
+ Misses        18480    18293     -187     
+ Partials       1316     1309       -7     

Flag	Coverage Δ		*Carryforward flag
access-control-service	71.42% <ø> (-3.36%)	⬇️
agent-service	34.36% <ø> (ø)		Carriedforward from a4153ca
amber	53.93% <ø> (+0.01%)	⬆️
computing-unit-managing-service	1.65% <ø> (ø)
config-service	57.35% <100.00%> (-1.22%)	⬇️
file-service	57.06% <ø> (ø)
frontend	47.42% <100.00%> (-0.08%)	⬇️
pyamber	90.70% <ø> (-0.09%)	⬇️	Carriedforward from a4153ca
python	90.74% <ø> (ø)		Carriedforward from a4153ca
workflow-compiling-service	58.69% <ø> (ø)

*This pull request uses carry forward flags. Click here to find out more.

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[github-actions]

✅ No material benchmark regressions detected

🟢 12 better · 🔴 0 worse · ⚪ 3 noise (<±5%) · 0 without baseline

CI benchmark results are noisy; treat <±5% as noise unless repeated.

Dashboard · Run

	config	throughput	MB/s	latency	max Δ latest / 7d
🟢	bs=10 sw=10 sl=64	390	0.238	25,233/35,168/35,168 us	🟢 -8.3% / ⚪ within ±5%
🟢	bs=100 sw=10 sl=64	919	0.561	105,293/133,992/133,992 us	🟢 +26.1% / 🟢 -8.3%
🟢	bs=1000 sw=10 sl=64	1,118	0.682	894,696/941,525/941,525 us	🟢 +18.1% / 🟢 +10.7%

Baseline details

Latest main 7ae9b35 from 2026-06-13T00:44:28.840Z

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	390 tuples/sec	394.18 tuples/sec	400.34 tuples/sec	-1.1%	-2.6%
bs=10 sw=10 sl=64	MB/s	0.238 MB/s	0.241 MB/s	0.244 MB/s	-1.1%	-2.6%
bs=10 sw=10 sl=64	p50	25,233 us	24,805 us	24,191 us	+1.7%	+4.3%
bs=10 sw=10 sl=64	p95	35,168 us	38,345 us	36,018 us	-8.3%	-2.4%
bs=10 sw=10 sl=64	p99	35,168 us	38,345 us	36,018 us	-8.3%	-2.4%
bs=100 sw=10 sl=64	throughput	919 tuples/sec	729.17 tuples/sec	867.19 tuples/sec	+26.0%	+6.0%
bs=100 sw=10 sl=64	MB/s	0.561 MB/s	0.445 MB/s	0.529 MB/s	+26.1%	+6.0%
bs=100 sw=10 sl=64	p50	105,293 us	133,219 us	114,874 us	-21.0%	-8.3%
bs=100 sw=10 sl=64	p95	133,992 us	173,178 us	142,264 us	-22.6%	-5.8%
bs=100 sw=10 sl=64	p99	133,992 us	173,178 us	142,264 us	-22.6%	-5.8%
bs=1000 sw=10 sl=64	throughput	1,118 tuples/sec	946.3 tuples/sec	1,010 tuples/sec	+18.1%	+10.7%
bs=1000 sw=10 sl=64	MB/s	0.682 MB/s	0.578 MB/s	0.616 MB/s	+18.1%	+10.7%
bs=1000 sw=10 sl=64	p50	894,696 us	1,059,718 us	995,071 us	-15.6%	-10.1%
bs=1000 sw=10 sl=64	p95	941,525 us	1,104,221 us	1,046,228 us	-14.7%	-10.0%
bs=1000 sw=10 sl=64	p99	941,525 us	1,104,221 us	1,046,228 us	-14.7%	-10.0%

Raw CSV

config_idx,batch_size,schema_width,string_len,num_batches,total_ms,total_tuples,total_bytes,tuples_per_sec,mb_per_sec,lat_p50_us,lat_p95_us,lat_p99_us
0,10,10,64,20,512.23,200,128000,390,0.238,25233.13,35167.89,35167.89
1,100,10,64,20,2176.11,2000,1280000,919,0.561,105292.72,133991.67,133991.67
2,1000,10,64,20,17885.95,20000,12800000,1118,0.682,894695.81,941525.09,941525.09